Update 3.20pm: So-called Islamic State has been blamed for the Istanbul suicide bomb that killed 10 at popular tourist site.
At least nine of the dead were German. Fiftenn other people were injured, Turkish officials said.
Prime minister Ahmet Davutoglu said IS was behind the suicide attack, adding that Turkey is determined to battle the militant group until it no longer “remains a threat” to the country or the world.
Turkey’s state-run news agency said Mr Davutoglu held a telephone conversation with German chancellor Angela Merkel to express his condolences.
A senior government official confirmed that most of the victims were German. Ms Merkel had earlier said they were part of a German travel group.
“I strongly condemn the terror incident that occurred in Istanbul, at the Sultanahmet Square, and which has been assessed as being an attack by a Syria-rooted suicide bomber,” president Recep Tayyip Erdogan said.
Deputy prime minister Numan Kurtulmus said the bomber was a 28-year-old Syrian national whose “connections” were being investigated. It was unclear whether the death toll of 10 included the bomber.
Update 1.45pm: A Syrian suicide bomber has detonated a bomb in a historic district of Istanbul popular with tourists, killing at least 10 people and wounding 15 others, Turkish President Recep Tayyip Erdogan said.
Mr Erdogan said in televised remarks that Turks and foreigners were among the dead in the explosion in the Sultanahmet district.
“I strongly condemn the terror incident that occurred in Istanbul, at the Sultanahmet Square, and which has been assessed as being an attack by a Syria-rooted suicide bomber,” Mr Erdogan said.
Deputy prime minister Numan Kurtulmus said the bomber was a 28-year-old Syrian national, and most of the people who died were foreigners.
The explosion, which could be heard over a wide area, hit a park that is home to a landmark obelisk, 30 yards from the historic Blue Mosque.
Turkey’s Dogan news agency reported that one Norwegian and a Peruvian were among the wounded, and Seoul’s Foreign Ministry said one South Korean had a finger injury.
At least nine of the wounded were German nationals.
German Chancellor Angela Merkel, speaking at a news conference in Berlin, said Germans from a group travelling together could also be among the dead.
“Today Istanbul was hit, Paris has been hit, Tunisia has been hit, Ankara has been hit before,” Ms Merkel said. “International terrorism is once again showing its cruel and inhuman face today.”
Update 12.35pm: A Syria-linked suicide bomber is believed to be behind a blast in Istanbul that killed 10 people and wounded some 15 others, the Turkish president has said.
Recep Tayyip Erdogan said in televised remarks on Tuesday that both Turks and foreigners were among the dead. He did not provide details.
A government official earlier said the explosion was believed to be “terror-linked”.
The blast, which could be heard over a wide area, hit a park that is home to a landmark obelisk, 30 yards from the historic Blue Mosque.
Turkey’s Dogan news agency reported that at least six Germans, one Norwegian and a Peruvian were among the wounded, and Seoul’s Foreign Ministry said one South Korean had a finger injury.
Police sealed off the area, barring people from approaching in case of a second explosion, and a police helicopter hovered overhead.
The Sultanahmet neighbourhood is Istanbul’s main sightseeing area and includes the Topkapi Palace and the Hagia Sophia museum.
Earlier:At least 10 people have been killed in an explosion in the historic Sultanahmet district of Istanbul, the city’s governor’s office has said.
Fifteen other people were injured, according to a statement.
The cause of the explosion is under investigation, but state-run TRT television said it was probably caused by a suicide bomber.
The Department of Foreign Affairs is urging any Irish people caught up in the blast to follow instructions from security personnel.
NTV television said the explosion happened near a park which is home to a landmark obelisk.
Several police and medics were sent to the area, which was sealed off by police amid fears of a second explosion.
— Bora Bayraktar (@Bora_Bayraktar) January 12, 2016
The Sultanahmet area is Istanbul’s main sight-seeing district and includes the Topkapi Palace and Blue Mosque.
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,” Mr Koroglu said. “Buildings rattled from the force of the explosion.”
Turkey suffered two major bomb attacks last year.
More than 30 people were killed in an Islamic State suicide attack in the town of Suruc, near the border with Syria, in July.
In October, two suicide bombs outside Ankara’s main train station as people gathered for a peace rally killed more than 100 people.
The prosecutor’s office said that attack was carried out by a local Islamic State cell.