An explosion at the heart of Istanbul's historic Sultanahmet tourist district which killed at least 10 people and wounded 15 on Tuesday 12 January may have been caused by a suicide bomber according to an eyewitness.

Murat Manaz who claimed he witnessed the blast described what he saw: "It was a suicide bomb, yes. I went there and saw it and came back to the hotel. There was chaos. Everybody was running somewhere. Policemen did not see this coming. They were sad but at the same time they were trying to evacuate the area because they said there was a possibility that a second bomb could go off. The square was completely evacuated," he said.

The Istanbul governor's office said the authorities were investigating the type of explosives used and who might have been responsible for the attack. It said 10 people had been killed and 15 wounded but gave no further details. Several bodies lay on the ground in the Sultanahmet square, close to the Blue Mosque, a tourist hotspot in Turkey's most populous city.

The attack at the heart of one of the world's most visited cities comes as Turkey battles Kurdish militants in its southeast region and Islamic State insurgents just across its southern borders in Syria and Iraq.

There was no immediate claim of responsibility but Kurdish, leftist and Islamist militants have all carried out attacks in Turkey in the past. Turkey's AHaber television said the blast may have been caused by a suicide bomber but this has not been independently verified.

Turkey has become a target for Isis, with two bombings last year blamed on the radical Sunni Muslim group.