A gunman dressed like Santa Claus is believed to have attacked one of the most iconic nightclubs in Turkey’s Istanbul soon after midnight Sunday. The club, which was packed with a crowd of over 500 people on the eve of new year, saw the assailant, armed with a long-barreled weapon, opening fire on civilians. Before entering, he killed a policeman and a civilian. At least 39 people lost their lives and 40 other were wounded.

The city’s Governor Vasip Sahin termed the incident a “terror attack” but shed no light on who may have carried it out. “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,” he told reporters. Sahin said there was only one attacker but other reports, including on social media, suggested there may have been at least two.

The club popular with locals and foreigners alike, overlooks the Bosphorus Strait separating Europe and Asia in the Ortakoy district, a neighbourhood on the city’s European side nestled under one of three bridges crossing the Bosphorus and home to nightclubs, restaurants and art galleries. Some of the party-goers jumped into the waters of the Bosphorus to save themselves and were rescued by police.

Security measures had been heightened in major Turkish cities, with police barring traffic leading up to key squares in Istanbul and the capital, Ankara. In Istanbul, 17,000 police officers were put on duty, some camouflaged as Santa Claus or street vendors.