Istanbul tourist district hit by deadly blast
The explosion occurred at about 10.20am local time on Tuesday morning. In a statement, the Istanbul governor's office said 10 people were killed and 15 were injured.
"Investigations into the cause of the explosion, the type of explosion and perpetrator or perpetrators are underway," it said in a statement quoted by the Dogan news agency.
Turkey explosion: Deadly blast strikes Istanbul tourist district
Foreign tourists are believed to be among the casualties.
Turkish President Recep Tayyip Erdogan said during a speech in Ankara that a Syria-linked suicide bomber was believed to be behind the blast.
There was no immediate claim of responsibility.
Turkey's Prime Minister Ahmet Davutoglu has convened an emergency security meeting of key ministers and officials.
Following 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.
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.
"Witnesses have said that the blast was heard from other neighbourhoods," he said. "Witnesses said that the ground shook."
Rende said police were conducting searches outside of the cordoned off area, in case a second bomber was involved.
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."
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.
Turkey has become a target for the Islamic State of Iraq and the Levant (ISIL), with two bombings last year blamed on the armed group, in the town of Suruc near the Syrian border and in the capital Ankara. The latter killed more than 100 people.
Violence has also escalated in the mainly Kurdish southeast since a two-year ceasefire collapsed in July between the state and the Kurdistan Workers Party (PKK) armed group, which has been fighting for three decades for Kurdish autonomy.
die in attacks on Iraqi casino and mall
|Gunmen charged into the mall after a car bomb exploded outside the building, in the largely Shia Muslim area of New Baghdad [AP]|
At least 32 people were killed and 58 injured in an attack on the al-Jawhara shopping centre in the capital, Baghdad, on Monday, according to police sources.
The assailants charged into the mall after a car bomb exploded outside the building, located in the predominantly Shia neighbourhood of New Baghdad.
Wary Iraqis say US-led air strikes on ISIL are not working
Police regained control of the mall and officials said that all attackers had been killed.
A senior security official told state television that there were no hostages, rejecting reports that there had been people held.
The Islamic State of Iraq and the Levant (ISIL) group claimed responsibility for the attack, as well as for a later attack in Diyala province.
Seven others were killed in a separate bombing in Baghdad, which has not been claimed by any group so far.
In the town of Muqdadiya in Diyala province, 80km northeast of Baghdad, a twin suicide bombing killed another 42 people at a cafe.
The second bomb went off as medics and civilians gathered at the site of the first blast.
Monday's attacks exacted the biggest death toll in the country in three months.