Six others who also appeared before the court in Istanbul were set to be released, Dogan added.
Authorities have said the attack was the work of a Syrian bomber from the Islamic State group.
Ten German tourists were killed and another 17 people wounded in the bombing in the historic centre of Istanbul near the Blue Mosque and the Hagia Sophia, the towering former Byzantine church that is now a museum.
Turkish authorities have identified the bomber as a 28-year-old Syrian who entered Turkey on January 5 posing as a refugee, with Prime Minister Ahmet Davutoglu saying the man was a member of IS.
The suspects, whose nationalities were not disclosed, were also said to have links to the IS group.
Ankara has often been criticised by its Western allies for not doing enough to combat IS jihadists who have seized swathes of territory in neighbouring Syria as well as Iraq.
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Authorities have said the attack was the work of a Syrian bomber from the Islamic State group.
Ten German tourists were killed and another 17 people wounded in the bombing in the historic centre of Istanbul near the Blue Mosque and the Hagia Sophia, the towering former Byzantine church that is now a museum.
Turkish authorities have identified the bomber as a 28-year-old Syrian who entered Turkey on January 5 posing as a refugee, with Prime Minister Ahmet Davutoglu saying the man was a member of IS.
The suspects, whose nationalities were not disclosed, were also said to have links to the IS group.
Ankara has often been criticised by its Western allies for not doing enough to combat IS jihadists who have seized swathes of territory in neighbouring Syria as well as Iraq.
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