The German Foreign Ministry said ten of those killed in the attack on Tuesday were German, without specifying if they accounted for all the victims.
Speaking in Istanbul, where he had visited the wounded in hospital, de Maiziere said there was “no indication” the attack specifically targeted Germans, saying there was no need to cancel travel plans.
“It was an attack against humanity,” he said. “I see no reason to refrain from trips to Turkey.”
But the German foreign ministry has advised its nationals to keep away from large groups in public places and tourist attractions in Istanbul.
German tourism giant TUI said customers who had booked trips to Istanbul can switch destination without paying a penalty.
String of bombings
Turkey has been hit by a string of deadly attacks blamed on jihadists over the last year, including a double suicide bombing in October in Ankara that killed more than 100 people.
A car bomb attack on Wednesday night, which was been attributed to Kurdish militants, killed five and injured 39 at a police station in southeast Turkey, officials said on Thursday.
But Tuesday's bombing was the first time in recent memory that tourists had been targeted in the heart of Istanbul.
The bomber, identified as Nabil Fadli, detonated his charge in Sultanahmet Square, home to Turkey's most visited historic sites including the Ottoman-era Blue Mosque and Hagia Sophia church.
The explosion went off by the Obelisk of Theodosius, a monument from ancient Egypt, one of the city's most iconic landmarks.
Police on Wednesday removed a cordon preventing access to the area of the attack, which was quickly thronged by media and some tourists, an AFP correspondent said.
After the cordon was removed, Turkish Prime Minister Ahmet Davutoglu, his wife Sare and de Maiziere placed red roses by the Obelisk, which appeared to have sustained no damage in the bombing.
Others wrapped football scarves around the railings from popular German teams including Bayern Munich and Borussia Dortmund, an AFP correspondent said.
The blast left 15 people wounded, most of them Germans but also Norwegians, Peruvians and at least one Turk. Berlin said seven injured Germans were being treated in hospital, five of them in intensive care.
The tourists were part of a group of 33 who had been staying at a boutique hotel in the upmarket Galata district and had been bussed to Sultanahmet that morning, media reports said.
“I saw the young man pull the pin and I shouted 'run!' in German. Then we started to run away, and the bomb instantly exploded,” the group's tour guide Sibel Satiroglu told investigators, the Hurriyet newspaper said.
Five suspects arrested
Turkey said Wednesday it had arrested a total of five suspects over the deadly suicide bombing.
Ankara has said that Tuesday's strike was perpetrated by a 28-year-old Syrian who belonged to the group Isis and had recently entered Turkey from Syria as a migrant.
Turkish security forces over the last days also rounded up 74 suspected Isis members across the country, state media said, but it was not clear if any were directly connected to the Istanbul bombing.
Davutoglu said that the bomber had not been on any wanted lists, but was registered entering Turkey from Syria as one of over 2.2 million Syrian refugees fleeing their nation's almost five-year civil war.
“This person was not being followed (as a wanted suspect). This person entered Turkey as an ordinary migrant,” said Davutoglu. “All his links will be worked out now.”
“Turkey is working to find the true actors behind this attack where Daesh (Isis) was used as a subcontractor,” he added, without explaining further.
The Sabah daily said the bomber had entered Turkey as a refugee from Syria on January 5th. He was then fingerprinted by the Turkish migration service, but the authorities insisted he had not been on any wanted list.
The Hurriyet daily said Turkey's spy agency had twice issued warnings over the risk of a suicide attack in Istanbul.
Since Tuesday's attack, the German Foreign Ministry has warned travelers that “across the country, continued political tensions and violent confrontations can be expected”.