Turkey has identified the gunman who killed 39 people when he opened fire in a crowded nightclub in Istanbul during the early hours of New Year's Day, according to Foreign Minister Mevlut Cavusoglu.

Speaking on television with the state-run Anadolu news agency, the minister did not give the suspect's name, but authorities have released a photo of the suspect, who remains at large.

"The identity of the person carrying out the attack ... has been determined," Cavusoglu said, without elaborating.

Turkish authorities have detained at least 43 people as part of their investigation into the attack.

Five of them are reportedly members of the so-called "Islamic State" (IS) militant group, which has sought to carve out a caliphate in neighboring Iraq and Syria.

IS in Turkey

IS has claimed responsibility for the massacre at Istanbul's upscale Reina nightclub. This marks the first time the militant group has claimed responsibility for a mass attack inside Turkey.

At least 27 of the 39 victims were foreign nationals from across the Middle East, including Iraq, Israel, Jordan, Lebanon, Morocco and Tunisia.

Turkish media have reported that the attacker moved to Istanbul from the central city of Konya, about 600 kilometers (375 miles) southeast of Istanbul to carry out the attack. Media reports claim he moved with his wife and two children so as not to attract attention.

Other local press reports said the gunman appeared to be well-trained in guerrilla warfare and may have been trained in Syria while fighting for IS. He killed two people, including a police officer, at the entrance to the nightclub. Once inside he began firing his military-style assault rifle, reportedly reloading as many as six times before escaping.

bik/kms (Reuters, AFP, dpa)