An attack at an Istanbul nightclub early Sunday killed at least 39 people and wounded at least 69.

Turkey's Interior Minister Suleyman Soylu said at least 16 of the dead were foreign nationals, without providing information on their nationalities. Five of the victims were identified as Turkish nationals while authorities were still trying to identify 18 of the victims. At least 69 people were being treated in hospitals, four in serious condition, Soylu said.

Istanbul Governor Vasip Sahin called the incident a "terror attack" and said the attacker shot and killed a police officer and a civilian before entering the club.

"Unfortunately [the attacker] 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.

The shooting occurred at the popular Reina nightclub in the city's Ortakoy neighbourhood, which sees hundreds of people each night and usually features heavy security, CBC's Nil Koksal reports. Dozens of ambulances were at the scene.

Soylu said the shooter was still on the run, adding: "efforts to find the terrorist are continuing."

The club is located close to recent suicide attacks that killed dozens near a soccer stadium.

Istanbul had already been under heavy security surveillance during the festivities, with police mounting machine-guns and armoured vehicles parked on the streets.

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

Ankara and Istanbul have been targeted by several attacks in 2016 carried out by ISIS group or Kurdish rebels, killing more than 180 people.

Canada's Minister of Foreign Affairs Stéphane Dion denounced the "horrendous attack" on Twitter and offered his condolences to the families of the victims.

Canadians in Istanbul were urged to avoid the area and contact consular assistance in the case of an emergency.

The White House condemned what it called a "horrific terrorist attack" and offered U.S. help to Turkey.

White House spokesman Eric Schultz said President Barack Obama was briefed on the attack by his national security team and asked to be updated as the situation developed. Obama is vacationing in Hawaii this week with his family.

White House National Security Council spokesman Ned Price said the attack on "innocent revellers" celebrating New Year's shows the attackers' savagery. He said the U.S. was sending thoughts and prayers to the relatives of those killed.