AT least 39 people been killed – including 16 foreigners – after a gunman stormed a popular nightclub in the early hours of the morning, according to reports.
Initial reports suggested there may have been two gunmen – but security sources now believe one attacker is responsible.
It is understood between 500 and 600 people were partying in the popular Reina club at the time of the attack.
A police officer and a Turkish international footballer are reportedly among the 39 dead.
The British Foreign Commonwealth Office hare trying to find out if Brits were killed or were injured in the attack.
A spokesman added: “We are in touch with the local authorities following reports of an incident at a night club in Istanbul.”
Reina is one of Istanbul’s best-known nightclubs and popular with tourists and locals.
Istanbul Governor Vasip described the gunman as a “terrorist” as he spoke to reporters at the scene.
He added: “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.
No terror group have claimed responsibility so far.
Dozens of ambulances and over 25,000 armed police have responded to the scene.
The gunman was reportedly dressed as Santa Clause and is believed to still be on the run.
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Sinem Uyanik, whose husband was wounded in the attack, said:”Before I could understand what was happening, my husband fell on top me.
“I had to lift several bodies from on top of me before I could get out.”
Her husband Lutfu Uyanik was wounded in the attack – but was not in serious condition.
Local reports say panicked party-goers jumped into the Bosphorus river, which runs near the club, to escape the attack.
The White House has issued a statment saying President Barrack Obama – who is away on holiday in Hawaii – has directed his team to provide assistance to Turkish authorities following the attack.
White House spokesman Eric Schultz said: “This afternoon [Saturday] the president was briefed by his national security team on the attack in Istanbul.
“The president expressed condolences for the innocent lives lost, directed his team to offer appropriate assistance to the Turkish authorities, as necessary, and keep him updated as warranted.”
It comes after Turkey brought in the new year just hours ago.