The video broadcast on Turkish television shows the alleged gunman filming himself with a cellphone at Istanbul's Taksim square. It wasn't immediately clear if it was filmed before or after the New Year's massacre at the Reina nightclub.
No details have been released as to why the authorities might think the man on the video is a suspect in New Year's attack, or how the footage was obtained.
The Islamic State group claimed the attack yesterday, saying a "soldier of the caliphate" had carried out the mass shooting in response to Turkish military operations against IS in northern Syria.
There were conflicting reports over the gunman's identity.
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Haber Turk newspaper today said the man is thought to be a member of China's Muslim Uighur minority. Without citing a source, the newspaper said he had arrived in the Turkish city of Konya with his wife and two children in order not to raise suspicions. His family members were detained, the newspaper said.
The mass shooting follows more than 30 violent acts that have rocked NATO member Turkey in 2016.
Turkey launched an offensive to northern Syria in August in a bid to clear a strategic border area of IS militants and contain the gains of Kurdish fighters. Turkish jets are regularly bombing IS targets in the Syrian town of al-Bab as Turkish-backed Syrian opposition force try to capture it from the extremists.
Seven of the nightclub victims were from Saudi Arabia; three each were from Lebanon and Iraq; two each were from Tunisia, India, Morocco and Jordan. Kuwait, Canada, Israel, Syria and Russia each lost one citizen.
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