Turkish police have launched raids in Istanbul and arrested 12 people, as the hunt for an attacker who killed 39 people in a nightclub intensifies, according to a BBC report.
Police have released new images said to be of the suspect but have not yet named him.
There are some reports in Turkish media that the authorities know the man’s identity but have not made it public.
Deputy Prime Minister Numan Kurtulmus said authorities had fingerprints and a basic description, and vowed to “speedily” identify the suspect.
Some 600 revellers were in the Reina nightclub early on Sunday when the gunman attacked.
The Islamic State (IS) group said it was behind the attack.
Turkish media reports quote police sources as saying he may have been from Uzbekistan or Kyrgyzstan.
Police are investigating whether the suspect belongs to an IS cell blamed for an attack in June on Ataturk airport in Istanbul.
Reports suggest he travelled to Turkey with his wife and two children in November to avoid detection, and that his family are among those detained.
Mr Kurtulmus said the nightclub attack was a “message” against Turkey’s operations in Syria but that they would not be affected.