At least 35 people have been killed and 40 wounded in an attack at a nightclub in Istanbul.

Istanbul Governor, Vasip Sahin, said a single shooter was responsible and described the incident as a "terrorist attack", without saying who may have carried it out.

"A terrorist with a long-range weapon...brutally and savagely carried out this incident by firing bullets on innocent people who were there solely to celebrate the New Year and have fun," he told reporters at the scene.