Turkey has arrested a number of people of Uighur origin over a deadly nightclub attack that killed 39, the state-run news agency reports.

Those detained are believed to have come from China's Xinjiang region with ties to the attacker, Anadolu says.

Deputy Prime Minister Veysi Kaynak also said the suspect was probably Uighur, and acted alone but may have had help.

Police have already detained dozens over the deadly new year attack, but the main suspect remains on the run.

So-called Islamic State (IS) says it carried out the attack over Turkey's military involvement in the Syrian civil war.

The authorities have reportedly tightened security at Turkey's land borders and airports to prevent the attacker from fleeing the country.

Turkish media have run images of a suspect, saying the pictures were handed out by the police. But the police have given no official details.

The Turkish foreign minister has said the authorities have identified the attacker, but has not given further details.

'Aiding and abetting'

Special forces made the early morning arrests at a housing complex in Selimpasa, a coastal town on the outskirts of Istanbul, after police were reportedly tipped off that individuals linked to the attacker were in the area.

Uighurs were among those arrested - the number was not confirmed - on suspicion of "aiding and abetting" the gunman, the Anadolu news agency reports.

The Uighurs are a Muslim, Turkic-speaking minority in western China, with diaspora communities across central Asia and Turkey.

At least 39 people were already in custody over suspected links to the attack, many of whom were picked up in an earlier police operation in Izmir, western Turkey.

Several families had recently travelled there from Konya, a central city where the main suspect was said to have stayed for several weeks before the attack.

Separately, Deputy Prime Minister Veysi Kaynak told Turkish broadcaster A Hamer that the authorities knew where the suspect, who he described as "specially trained", was hiding, without giving further details.

Witnesses to the new year attack said more than 100 rounds of bullets were fired which, the BBC's security correspondent Frank Gardener says, indicates the gunman had at least some rudimentary military training.

Mr Kaynak expressed confidence in the Turkish police operation but said he could not rule out the possibility of the attacker fleeing the country.

No Kyrgyz connection

Previous media reports incorrectly suggested the culprit was a national from Kyrgyzstan, after a passport photo claiming to show the attacker was circulated.

It later emerged the passport belonged to someone unrelated to the attack.

Kyrgyzstan's embassy in Turkey has since asked the media to retract the reports and issue an apology.

More than half of those killed in Sunday's attack on Istanbul's popular Reina nightclub were foreigners, including citizens from Lebanon, Saudi Arabia, Israel, Iraq and Morocco.

The gunman managed to escape in the aftermath of the attack.

A day later, IS issued a statement saying "a heroic soldier" belonging to the group had carried out the attack in retaliation for Turkey's military role in northern Syria.

Mr Kaynak said on Thursday Turks were questioning the use of the country's Incirlik air base by both Nato and the US-led coalition launching air strikes on IS in Syria and Iraq.

Turkey launched a military operation in Syria in August to push back IS and Kurdish forces.

Some of Turkey's big cities have since been targeted in a number of bomb attacks by IS and by Kurdish militants.