What we know so far:
- A large truck drove into a crowded Christmas market in west Berlin at around 8.30pm on Monday evening.
- So far 12 people have been confirmed dead, and 48 have been injured. Over a dozen are in a critical condition.
- Police confirmed they believe the attack was deliberate, but said on Tuesday they might have arrested the wrong man.
- Prosecutors have now released the suspect.
- Police are telling Berliners to stay alert and to call them if they see anything suspicious.
- Chancellor Angela Merkel has said the attack was presumably an act of terrorism.
- Isis has claimed responsibility for the attack.
8.43pm From news agency AFP: A "soldier" of the Islamic State group carried out the truck attack, a news agency linked to the jihadists said.
"A soldier of the Islamic State carried out the Berlin operation in response to appeals to target citizens of coalition countries," the Isis-linked Amaq news agency said in a statement posted online.
The statement did not identify the attacker.
7.02pm Prosecutors have released the 23-year-old they arrested after the attack due to a lack of evidence against him.
The man was arrested after a witness chased the attacker through the Tiergarten park. It now seems he lost sight of the actual attacker and led police to the wrong man.
6.39pm Prosecutors have until midnight to seek a detention order for the suspect. According to German law suspects can only be detained until midnight of the day after their arrest without being brought before a judge.
Berlin's police chief Klaus Kandt has already said that the man probably wasn't the driver of the vehicle.
Several news organizations have reported that no traces of blood or gunfire residue have been found on his person, despite a murdered man with bullet wounds in his body being found in the cabin of the truck.
6.30pm President Barack Obama has called Angela Merkel to offer assistance and condolences following the deadly attack.
"The President offered his condolences, and those of the American people, for the horrific apparent terrorist attack," the White House said following the call late on Monday.
"The President reiterated the US offer of assistance and underscored that no attack could sway our determination - and that of our German allies - to defeat terrorism in all of its forms."
6.22pm Dortmund, a city in the western state of North Rhine-Westphalia, has banned trucks from driving through the city centre at between 6pm and 11pm until the end of the year. It has said the decision came in response to the events in Berlin.
6.09pm The Brandenburg Gate has been light up in the colours of the Berlin flag. It has also been light up in the colours of the German flag.
6.06pm A service has started in the Kaiser Wilhelm memorial Church in remembrance of the dead.
The attack took place just below the church which is on of the most iconic anti-war symbols in Germany. It's spire was damaged by Allied bombing in 1943 and has never been repaired.
At the service, Süddeutsche Zeitung's Thorsten Denkler tweets that "it is good that Muslims are also here."
4.54pm Police have announced some good news about victims of the attack.
"This gives us hope: 24 of the injured have already left hospital and are back with their families," they tweet.
Das macht uns Hoffnung, 24 Verletzte vom #Breitscheidplatz konnten die Krankenhäuser bereits verlassen & sind wieder bei ihren Angehörigen.— PolizeiBerlinEinsatz (@PolizeiBerlin_E) December 20, 2016
4.36pm UN Secretary-General Ban Ki-moon on Tuesday condemned the rampage and expressed his deepest sympathy and condolences to the families of the victims.
"The secretary-general condemns the terrorist attack in Berlin last night," said a statement from his spokesman.
He "hopes anyone involved in the commission of this appalling crime will be swiftly brought to justice," he added.
3.50pm Berlin's Christmas markets will not open on Tuesday, according to Spiegel. Across the rest of the country, Christmas markets will have strong security protocols in place.
3.38pm Berlin's police chief said on Tuesday that the "dangerous criminal" behind a deadly truck rampage at a Christmas market may still be at large, urging "heightened vigilance".
"It is the case that we may have a dangerous criminal in the area and that of course makes the public nervous," the police chief, Klaus Kandt, said after voicing doubts that a Pakistani asylum seeker in custody was behind the attack on Monday evening that killed 12 people.
"Of course we are boosting security measures. Heightened vigilance is also needed right now."
3.34pm Chancellor Angela Merkel has visited the scene of the attack along with Foreign Minister Frank Walter Steinmeier and Interior Minister Thomas de Meziere.
The Chancellor visited the area of the crime and was briefed by security personnel at the scene.
3.13pm Berlin police have tweeted a picture of officers observing the minute of silence which took place at 3pm. They said they are "deeply sad for the victims."
3.00pm Federal prosecutors are giving a press conference. They say the believe this was a terror attack. But they added that it is not clear whether it was carried out by just one or several people.
They also heavily hint that the person they have in custody was not involved, saying: "We must get used to the possibility that he is not the attacker".
Police pointed out that as yet no video has emerged taking credit for the attack.
After two attacks earlier this year - an axe attack in Würzburg in July and a suicide attack in Ansbach a week later - terror group Isis released videos purportedly of the attacker (in the Ansbach video the man's face was covered) one day after each incident.
2.47pm There is various information emerging relating to the suspect. To try to summarize:
- The Polish haulage company boss whose driver died in the vehicle claims a picture he saw of his driver shows that he was involved in a struggle and that he had suffered stab wounds.
- Police also report that the Polish man was shot.
- However it seems that investigators have not found gun discharge residue from a weapon on the suspect's clothes, nor have they found blood or any signs that he was involved in a struggle. That is according to information Spiegel has from high ranking police officials.
- At the same time, according to DPA, blood-covered clothes were found in the vehicle, suggesting that the attacker could have changed what he was wearing after murdering the Polish driver.
2.32pm Germany's finance minister Wolfgang Schäuble has said he is "absolutely not shocked" by the attack," reports the Süddeutsche Zeitung.
"We always said this would reach us," the veteran politician reportedly said.
2.29pm There will be a minute of silence in Berlin at 3pm to remember the victims, city mayor Michael Müller has announced.
2.23pm Die Welt again have valuable information relating to the crime. They report on the November issue of the Isis magazine Rumiyah, which encouraged followers to use vehicles to attack crowds.
"A vehicle is one of the most secure and simple weapons that you can use against the Kuffar," the magazine reportedly advises.
2.01pm Police are also telling Berliners to stay alert, suggesting they believe the attacker could still be on the loose.
The temporary arrested suspect denies the offense.— PolizeiBerlinEinsatz (@PolizeiBerlin_E) December 20, 2016
Therefore we are particulary alert.
Please be also alert.#Breitscheidplatz
They are also telling people not to act like private detectives.
For your safety! In case of suspicious observations, please don't investigate on your own - it's our job.— PolizeiBerlinEinsatz (@PolizeiBerlin_E) December 20, 2016
1.58pm Die Welt is now reporting more on the investigation into the Pakistani man detained on suspicion of driving the truck.
They report that police have been unable to find any traces of blood on his clothes, which would be a logical consequence of having shot the Polish truck driver who was found dead in the passenger seat.
1.42pm Police now seem to be confirming the Die Welt report about having arrested the wrong man
"It is indeed uncertain that he was the driver," said police chief Klaus Kandt. "The initial evidence has been limited."
1:34 pm German daily Die Welt cites a police source as saying "the wrong man" is in custody, and the real driver of the truck may still be at large.
If the Welt report is accurate that means that an armed and dangerous man is on the run in Berlin.
Die Welt's source said: "This means we face a new situation. The real perpetrator is still armed and on the loose. He can still do more damage."
1.04pm The interior ministry has confirmed that the suspect has denied all responsibility for the attack.
12.59pm A photograph from Kassel in Hesse shows concrete blocks placed before the entrance to its Christmas market.
12.50pm The Central Council of Muslims (ZMD) has expressed its shock at the attack.
"The ZMD will do everything it can to ensure that the poisonous seed of panic, hate and strife between communities and religions cannot grow," it said in a statement.
12.30pm In Dresden, city authorities have started erecting concrete blocks at the entrance to the city's famous Striezelmarkt due to "an altered security situation."
12.03pm The 23-year-old suspect is denying having any association to the attack, DPA reports on information from investigators.
11.49am The conversation in Germany is now turning to how to prevent further attacks. A discussion on N-tv recognized the relative simplicity of attacking a Christmas market, which are dotted around town centres up and down the country.
One possible precaution brought up by journalists is the erection of concrete blocks at the entrances to of Christmas markets to stop people driving into them.
11.41am Police say they have upped their presence in Berlin as a precaution.
11.40am France's far right have pointed the finger of blame at Germany's open door policy towards refugees.
French presidential candidate Marine Le Pen released a statement saying: “How many massacres and deaths will be necessary for our governments to stop bringing in a considerable number of migrants into our communities without borders, when we know that Islamist terrorists are among them?
11.26am Russian President Vladimir Putin on Tuesday expressed shock at the "brutality and cynicism" of the apparent attack on a Christmas market in Berlin.
"This crime committed against peaceful civilians shocks with its brutality and cynicism," Putin said in a message of condolence to Germany's leaders released by the Kremlin.
11.24am broadcaster N-tv is reporting that 18 people are still in a critical situation in hospital, several of whom have life-threatening injuries.
11.07am Angela Merkel has spoken to the nation, saying "we should assume this was a terror attack given what we know".
She added that it would be "particularly disgusting" if it turned out the attacker was an asylum seeker, saying such an act would be an insult to all those who helped refugees and to all those who genuinely need Germany's protection.
Merkel also thanked investigators and emergency services for their efforts overnight.
She said that "fear of evil" must not stop people from going about their daily lives and enjoying places like Christmas markets where they can meet with family and friends.
The Chancellor has also said that she will go to Breitscheidplatz this afternoon to pay her respects.
10.54am The interior ministry says that Christmas markets should stay open in the wake of the attack.
"Regardless of what we may learn about the exact motives of the assailant, we must not let our free way of life to be taken from us," the interior ministry statement said.
10.52am The interior ministry is now describing the incident as an attack.
10.48am The Polish man who was found dead in the passenger seat had been shot, a state official has said. Karl-Heinz Schröter, interior minister in Brandenburg, said that the Polish man was a victim not a perpetrator.
10.29am Yvette, a doctor who works in the area of the attack and who was at the Christmas market a few hours before it happened, has spoken to The Local:
"You aren't safe anywhere anymore, I've lived with this thought for a few years now. But if I let it get to me I wouldn't go outside," she said.
"A few weeks ago there was a huge police operation under our office that involved the army too. They arrested drug dealers who were casually drinking coffee downstairs.
"We shut all our windows and closed ourselves in with our patients. We could see them armed with machine guns. To experience something like that makes you even more scared.
"I'm just grateful that I chose to visit the market at a different time."
"I hope that the person can live with so many people's lives on their conscience - I certainly couldn't."
10.22am Frauke Petry, leader of the rightwing Alternative for Germany, has said that Germany is "no longer safe", also blaming the government for what happened.
"The milieu in which such actions can thrive was negligently and systematically imported into Germany over the past 18 months."
She called for Germany's borders to be "properly controlled again".
10.12am The security cabinet, consisting of Chancellor Angela Merkel, her defence, foreign and interior ministers, plus other important government figures, is to meet at 11.30 am
10.05am Angela Merkel is to give a press conference at 11.00 am about the incident. She had already announced she was cancelling a trip to her constituency in northeastern Germany.
9.58am According to Spiegel the suspect went under the names Naved B. and Navid B. and received permission to stay in Germany in June.
9.53am. The Swiss government has sent its condolences to Germany.
“Deeply affected by the tragic events in Berlin. Our thoughts are with the victims and their families,” tweeted Swiss President Johann Schneider-Ammann.
9.43am Die Welt is reporting that police were helped in their attempts to catch the man by a courageous bystander who followed the driver as he fled the scene. Police caught the man soon after the attack.
9.21am A specialist police unit conducted searches on Monday morning in hangars at Berlin's old Tempelhof airport. The buildings now house the city's biggest asylum seeker accommodation.
The search began at 3am and ended at 8am. 250 officials took part in the search. Four young men were questioned but police made no arrests.
A man suspected of intentionally driving into a crowd at a Christmas market on Monday night was living in a Berlin asylum centre, intelligence sources told the DPA news agency.
Police have not confirmed the search at the former airport.