At least 35 people were killed and 40 wounded in a "terror attack" on an Istanbul nightclub on Sunday where people were celebrating the New Year, the city's governor said.

"Unfortunately, at least 35 of our citizens lost their lives. One was a police officer. Forty people are receiving treatment in hospitals," Vasip Sahin told reporters at the scene of the elite Reina nightclub on the Bosphorus in the city's European side, describing the incident as a "terror attack".

Many party-goers threw themselves into the Bosphorus in panic after the attack and efforts were underway to rescue them from the waters, NTV television said.