ISIS fanatics have claimed responsibility for the Istanbul nightclub atrocity as an international manhunt continues for the gunman who murdered 39 revellers.

Photos from inside Istanbul’s packed Reina club show partygoers celebrating moments before he stormed the venue.

The assassin calmly stepped out of a taxi outside the club before removing an AK-47 from his bag. CCTV footage then shows the man firing indiscriminately as he went on the five-and-a-half minute rampage.

Shocking new details of the attack, which also left 70 injured, emerged as the first funerals of victims were held last night.

ISIS this morning released a statement claiming it had carried out the attack.