Seven people have been detained in connection with a suicide bombing at the heart of Istanbul's historic district that killed 10 German tourists, Turkish Interior Minister Efkan Ala said on Thursday.
The bomber, identified as a member of Islamic State who had entered Turkey as a refugee from Syria, blew himself up on Tuesday among tourists visiting some of Istanbul's most popular attractions.
Fifteen people, mostly foreigners, were also wounded in the attack.
"The number of those detained in connection with Istanbul attack have reached seven. The investigation is underway in the most comprehensive way", Ala told reporters at an ambassadors' conference in Ankara.
Turkey was quick to identify the bomber, named by Turkish media as 28-year old Saudi-born Nabil Fadli, as the man who had given his fingerprints a week ago at an immigration center.
Prime Minister Ahmet Davutoglu said fragments of the bomber's skull, face and nails at the site of the blast matched his records.
Turkey, which like Germany is a member of the U.S.-led coalition against Islamic State in Syria and Iraq, has become a target for the radical Sunni militants.
It was hit by two major bombings last year blamed on the group. One was in the town of Suruc near the Syrian border and the other in the capital Ankara, where more than 100 people were killed in the worst attack of its kind on Turkish soil.
Dozens of tourists and Turks holding carnations have paid their respects at the blast scene on Thursday, near the Blue Mosque and Hagia Sophia, the top sites in one of the world's most visited cities.