ISTANBUL • A car bomb ripped through a police bus near Istanbul's historical centre yesterday, killing 11 people and adding to security concerns after a string of attacks in Turkey's biggest city.

The blast targeted a shuttle service carrying anti-riot police as it passed through the Beyazit district, close to many of the city's top tourist sites, Istanbul governor Vasip Sahin said on Turkish television.

Thirty-six people were wounded, three of them seriously, he said. The 11 people killed were seven officers and four civilians.

There was no early claim of responsibility, but President Recep Tayyip Erdogan hinted that the outlawed Kurdistan Workers' Party (PKK) was behind the attack.

Kurdish militants have repeatedly targeted Turkey's security forces, but the Islamic State in Iraq and Syria militant group has also staged several attacks in Turkish cities in the past year.

Reports said the explosion occurred close to the Vezneciler metro station, within walking distance of some of the city's main tourist sites, including the famed Suleymaniye Mosque.

The blast reduced the police vehicle to mangled wreckage and shattered windows in nearby shops. Several witnesses said that shots were heard afterwards, but there was confusion about whether the attackers had opened fire or whether police officers had been trying to protect colleagues.

"We were told that it was police trying to keep people away from the blast scene," said Mr Mustafa Celik, 51, who owns a tourism agency near the blast site. He said the impact of the explosion was like an earthquake.

"I felt the pressure as if the ground beneath me moved. I've never felt anything this powerful before," he said.

The attack occurred opposite an upscale hotel favoured by foreign tourists, the Celal Aga Konagi Hotel. The 16th-century Sehzade Mosque, considered one of the masterpieces of Ottoman architect Mimar Sinan, was also damaged.

The Singapore Ministry of Foreign Affairs said there are no reports of any Singaporeans affected by the incident. French President Francois Hollande condemned the attack as an "intolerable act of violence".

The bombing, on the second day of the Muslim holy month of Ramadan, is the latest in a string of attacks that have rattled citizens and damaged tourism.

Two blasts in Ankara claimed by the Kurdistan Freedom Falcons - a radical splinter group of the PKK - earlier this year claimed dozens of lives. Last month, at least eight people including soldiers were wounded by a remotely detonated car bomb targeting a military vehicle in Istanbul that was claimed by the PKK.

AGENCE FRANCE-PRESSE, REUTERS