In a statement, German federal prosecutors confirmed that three Syrian nationals had been arrested and their homes searched: 25-year-old Mahood B., 27-year-old Hamza C. and 31-year-old Abd Arahman A.K.
A further warrant was issued for a 25-year-old Syrian, Saleh A., currently under arrest in France.
The three arrested in Germany lived in North Rhine-Westphalia, Baden-Württemberg and Brandenburg.
Prosecutors said that two suicide bombers were to blow themselves up on Heinrich-Heine-Allee, a broad street with a number of public transport links including U-Bahn and tram stations.
Then the other attackers were supposed to kill more passers-by with rifles and explosives.
Plan years in the making
Saleh A. and Hamza C. travelled from Syria to Turkey in 2014 after their attack plan was approved by Isis leaders, prosecutors allege.
In 2015 they then travelled to Germany via the Balkans, where they made contact with a third Syrian, 31-year-old Abd Arahman A. K., an explosives expert sent to Germany by Isis in October 2014.
Abd Arahman had built explosives for Syrian terrorist organization Jabhat al-Nusra, and was to assemble the explosive vests for the suicide bombers, prosecutors say.
But before the plans could be realized, Saleh A. gave himself up to French security authorities on February 1st 2016.
French authorities informed German security services of the attack plan.
Federal prosecutors now aim to have Saleh A. extradited from France to face charges in Germany.
Security sources told Der Spiegel that there was no evidence the attack was to take place imminently.
Nor was there any link with the Euro 2016 football championship due to start in France in just over a week, federal prosecutors said.
All four men are accused of conspiring to commit a crime. Saleh A., Hamza C. and Abd Arahman A.K. are suspected of being members of Isis, which Germany classes as a foreign terrorist organization.
Mahood B., who prosecutors say joined the plot after the other conspirators had reached Germany, faces a charge of supporting a foreign terrorist organization.
Abd Arahman A.K. also faces a charge of preparing a serious violent crime against the state while in Syria.
German security authorities have long warned that the Federal Republic could be a target for terrorists.
In the wake of November's attacks in Paris that killed 130 people and wounded hundreds more, security policy specialist MP Stephan Mayer of the Christian Democratic Union told The Local that “Germany is just as much in the sights of the terrorists as France”.