Four people were arrested Thursday in connection with an armed attack on police outside the US consulate in Istanbul a day earlier, dpa reported.
Police were still searching for the man who drove the three suspected al-Qaeda militants to the consulate, the Anadolu news agency reported.
Interior Minister Besir Atalay told reporters in Istanbul that three people in Istanbul and one from outside the city were taken into custody on suspicion of being connected to the attack that left three gunmen and three police officers dead.
Anadolu later reported that a man had been arrested in the eastern Turkey city of Kars.
As funeral ceremonies for the three police officers took place in Istanbul, police were on high alert throughout the city searching for the driver of a grey Ford Focus that fled the scene of the gun fight that, according to witnesses, lasted between seven and eight minutes.
Armed with handguns and pump-action rifles the three assailants opened fire on a police post just metres away from the main gate of the consulate in Istanbul's Istiniye suburb.
Turkish media on Thursday reported that two of the three gunmen, all Turkish nationals, had received training at camps of the al-Qaeda terrorist network in Afghanistan.
No group has claimed responsibility for the attacks that US Ambassador to Turkey Ross Wilson on Wednesday described as a "dastardly and cowardly act."
Security was beefed up outside the consulate on Thursday with around 60 anti-riot police on guard. The US consulate flag flew at half-mast.