An explosion in the heart of Istanbul's historic Sultanahmet tourist district has killed at least 10 people and wounded 15, and some local media reports said a suicide bomber may have been responsible.
The blast took place around 10:20am on Tuesday (local time) in the Sultanahmet square, which is near the historic Blue Mosque, a major tourist area of Turkey's most populous city.
A statement from the Istanbul governor's office said at least 10 people have died in the blast and 15 are injured.
According to local media, foreign tourists from Germany and Norway are among the wounded. A tourist group from Germany was in the area at the time of the explosion, an official from a tour company told Reuters, but it was unclear whether any of them had been hurt.
Witnesses reported hearing a loud blast and video footage on the CNN Turk channel showed police and ambulances at the scene.
A witness told a Reuters correspondent that there were body parts at the scene, which police have sealed off in case of a second explosion. A police officer confirmed the witness' account.
The explosion was so forceful it rattled nearby buildings, another witness told the privately-run NTV television.
Local media said the blast was likely caused by a suicide bomber, but this was not independently confirmed.
Investigations are being conducted into the type of explosive which caused the blast and those responsible, the statement from the governor's office said.
The blast comes just over a year after a female suicide bomber blew herself up at a police station for tourists off the same square, killing one officer and wounding another. That attack was initially claimed by a far-left group, but later turned out to have been perpetrated by a woman with suspected Islamist militant links, officials said.
Kurdish, leftist and Islamist militants have all carried out attacks in Turkey in the past.
Turkey has also become a target for Islamic State, with two bombings last year blamed on the radical Sunni Muslim group, in the town of Suruc near the Syrian border and in the capital Ankara, the latter killing more than 100 people.
3 News / Reuters