A number of deaths have been reported after an explosion rocked central Istanbul’s historic Sultanahmet square, a major tourist attraction.

The explosion occurred at about 10.20am local time on Tuesday morning.

Turkey’s Haberturk television reported that at least eight people were killed in the explosion.

Ambulances rushed to the site in Sultanahmet square, close to the Blue Mosque and Hagia Sophia, in a major tourist area of Turkey’s most populous city, ferrying away the wounded as police cordoned off streets.

The cause of the explosion was not immediately clear.

Police are reportedly taking extra measures to protect people against the possibility of a second explosion.

Al Jazeera’s Emre Rende, reporting from Istanbul, said information was scarce immediately after the blast.

“Eyewitnesses have said that the blast was heard from other neighbourhoods,” he said.

Erdem Koroglu, who was working at a nearby office at the time of the explosion, told NTV television he saw several people lying on the ground following the blast.

“It was difficult to say who was alive or dead,” Koroglu said. “Buildings rattled from the force of the explosion.”

Turkey suffered two major bombing attacks last year. (Al Jazeera)