Turkish police carried out a dawn raid on the edge of Istanbul and detained suspects thought to be linked to the attack
A possible location for the suspect behind the Istanbul nightclub gun attack has been identified, Turkey's deputy PM has said.
Veysi Kaynak said the gunman was probably a member of the Uighur community - a primarily Muslim Turkic-speaking group who live in Eastern and Central Asia with the majority in the Xinjiang region of China.
In an interview with broadcaster A Haber, he said his government could not rule out the possibility that the attacker had fled the country, but said on Thursday that operations in Turkey were likely to be successful.
Mr Kaynak added that it was clear the attack was carried by one person, but he may have had help.
It comes after Turkish police carried out a dawn raid on the edge of Istanbul and detained suspects thought to be linked to the nightclub attack on New Year's Day, in which 39 people were killed.
Counter-terrorism police and special forces took part in the operation on a housing complex in Selimpasa, on the coast just west of Istanbul, following intelligence that individuals who may have helped the attacker were there.
The suspect, who is still at large, shot his way into the Reina nightclub and then opened fire with an automatic rifle, throwing stun grenades as he reloaded his weapon and shooting wounded people on the ground.
Among the victims were citizens from Lebanon, Saudi Arabia, Israel, Iraq and Morocco.
Islamic State claimed responsibility for the attack, claiming it was in revenge for Turkish military involvement in Syria.
Security sources have said the gunman may have been trained in Syria.
At least 36 people have been detained since the attack on Sunday, according to reports. Some of them are also members of the Uighur community.
Security on Turkey's land borders has been tightened over fears the attacker planned to flee the country, the Dogan news agency reported.
It said checkpoints will be set up to search vehicles and people leaving through border crossings in Edirne, western Turkey, and on into Greece and Bulgaria.