At least 35 people have been killed and dozens more wounded in an attack at a popular nightclub in Turkey’s most populous city, Istanbul.

Turkish media reports say an armed man opened fire on people taking part in new year celebrations at the Reina nightclub in Istanbul’s Besiktas district.

Another 40 people are reported to have been wounded in the attack at the night spot in Ortakoy neighbourhood.

Local reports said eight of those injured were in a critical condition.

The Reina lies on the shore of the Bosphorus Strait and is one of Istanbul’s best-known nightclubs, popular with locals and tourists alike.

Ortakoy is a cosmopolitan neighbourhood located under one of three bridges crossing the Bosphorus, and home to clubs, restaurants and art galleries.

The Reina nightclub in Ortakoy neighbourhood was packed with New Year’s revellers[Reuters]

The attacker shot his way into the Reina, which was packed with New Year’s revellers early on Sunday, reports said.

He shot a police officer and a civilian as he entered the Reina nightclub before opening fire at random inside.

Some survivors jumped into the waters of the Bosphorus to save themselves and were being rescued by police.

Dozens of ambulances and police vehicles were dispatched to the attack site in Ortakoy.

Al Jazeera’s Jamal Elshayyal, reporting from the scene, said he saw several survivors rushing to taxis to leave after belng cleared to leave the scene by police.

“What security services will be trying to ascertain is not only how many attackers there were but what kind of weapons were used and how they were able to overcome security precautions,” he said.

Vasip Sahin, the governor of Istanbul, said the incident was “a terror attack” targeting innocent people who were at the club to celebrate the new year.

“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,” he said at the scene.

About 700 people were thought to have been in the nightclub when the attack happened at around 1:15am local time, broadcaster CNN Turk said, citing officials.

Sunday’s shooting is the latest in a long line of attacks to hit Istanbul [Osman Orsal/Reuters]

There has been no claim of responsibility so far for the attack, but experts say the needle of suspicion points at the Islamic State of Iraq and the Levant (ISIL) group, which has repeatedly targeted civilians in Turkey in recent months.

Al Jazeera’s Sinem Koseoglu, reporting from Istanbul, said security services believed the timing and target of the attack suggested ISIL involvement.

The Reina nightclub is not only frequented by partygoers but also used as a venue by businessmen and diplomats to conduct meetings, she said.

The US President Barack Obama has offered his condolences and said his country’s intelligence services would help Turkish authorities investigate the attack.

Multiple threats

Turkey, part of the US-led coalition against ISIL, faces multiple security threats including fallout from the war in neighbouring Syria.

It has seen repeated attacks and bombings blamed on ISIL, also known as ISIS, as well as Kurdish fighters of the PKK in recent months.

The PKK and its affiliates are known to target mostly members of Turkey’s security forces rather than civilians.

The attack comes less than two weeks after the Russian ambassador to Turkey, Andrei Karlov, was shot dead by a lone gunman while giving a speech at an art gallery in Ankara.