ISTANBUL (AFP) - The attacker who shot dead 39 people on New Year's night at an Istanbul nightclub has been identified as an Uzbek militant who belongs to the extremist Islamic State in Iraq and Syria (ISIS) group, Turkish press reports said.

There had been confusion over the identity of the attacker - who remains on the run - with reports initially suggesting a Kyrgyz national and then a Uighur from China.

But intelligence services and anti-terror police in Istanbul have now identified the man as a 34-year-old Uzbek who is part of a Central Asian ISIS cell, the Hurriyet daily and other Turkish newspapers reported.

It said he has the code name of Ebu Muhammed Horasani within the ISIS extremist group. There was no official confirmation of the report.

The killer slipped into the night after killing 27 foreigners and 12 Turkish nationals at the Reina nightclub in Istanbul just 75 minutes into 2017.

Despite an intense manhunt, he remains on the run, with some reports saying that he is still believed to be in Istanbul.

Turkish police had last week released images of the alleged killer, including a chilling silent video he purportedly took in central Istanbul with a selfie stick.

Uzbekistan clamped down on militant Islam after the fall of the Soviet Union under the secular rule of its long-standing leader Islam Karimov who died in 2016.

ISIS militants from Central Asia, including Kyrgyzstan and Uzbekistan, as well as from Russia's Muslim regions of Dagestan and Chechnya are believed to have played a key role in the triple suicide bombings and gun attack at Istanbul's main airport in June.

The ISIS extremist group claimed the Istanbul nightclub attack, the first time it has ever clearly claimed a major attack in the country despite being blamed for several strikes including the airport bombings.