UPDATE | New Year's attack on packed Istanbul club leaves 35 dead

ISTANBUL (AP) — An assailant believed to have been dressed in a Santa Claus costume opened fire at a nightclub in Istanbul during New Year's celebrations, killing at least 35 people and wounding 40 others in what the province's governor described as a terror attack.

Gov. Vasip Sahin said the attacker, armed with a long-barreled weapon, killed a policeman and a civilian outside the club about 1:45 a.m. Sunday before entering and firing on people partying inside. He did not say who may have carried out the attack.

"Unfortunately [he] rained bullets in a very cruel and merciless way on innocent people who were there to celebrate New Year's and have fun," Sahin told reporters.

Private NTV news channel said the assailant entered the Reina nightclub, in Istanbul's Ortakoy district, dressed in a Santa Claus outfit.

Some customers jumped into the waters of the Bosporus to escape the attack, the report said. NTV television said some of the wounded were foreign nationals, without citing their nationalities.

The whereabouts of the assailant was not known and it was not clear if he had been caught.