ISTANBUL — A Syrian ******* ****** detonated a **** in a historic district of Istanbul popular with tourists Tuesday morning, ******* at least 10 people — at least nine of them German tourists — and wounding 15 others, ******* officials said.

Turkey’s state-run news agency said Prime Minister Ahmet Davutoglu held a telephone conversation with German chancellor Angela Merkel to express his condolences. A senior government official confirmed that most of the ******* were German. Merkel had earlier said they were part of a German travel group.

“I strongly condemn the ****** ******** that occurred in Istanbul, at the Sultanahmet Square, and which has been assessed as being an ****** by a Syria-rooted ******* ******,” President Recep Tayyip Erdogan said.

Deputy Prime Minister Numan Kurtulmus said the ****** was a 28-year-old Syrian national whose “connections” were being investigated.

It was unclear whether the ***** toll of 10 included the alleged ******.

Merkel, speaking at a news conference in Berlin, decried the ******.

“Today Istanbul was hit; Paris has been hit, Tunisia has been hit, Ankara has been hit before,” she said. “International ********* is once again showing its cruel and inhuman face today.”

The *********, which could be heard from several neighbourhoods, was at a park that is home to a landmark obelisk, some 25 metres (yards) from the historic Blue Mosque.

Turkey’s Dogan news agency reported that one Norwegian and one Peruvian were also among the *******, and Seoul’s Foreign Ministry told reporters via text message that a South Korean had a finger ******. The Norwegian Foreign Ministry told Norway’s news agency NTB that the Norwegian tourist was slightly hurt and was being treated in a local hospital.

Kurtulmus, the deputy premier, said two of the ******* were in serious condition.

Germany and Denmark have warned their citizens to avoid crowds outside tourist attractions in Istanbul.

There was no immediate claim of responsibility for the ******, although the Islamic State group was suspected. Kurdish militants and left-wing groups are active in Turkey.

Last year, Turkey agreed to take a more active role in the U.S.-led battle against the IS group. Turkey opened its bases to U.S. aircraft to launch air raids on the extremist group in Syria and has carried out a limited number of strikes on the group itself.

It has also moved to tighten security along its 900-kilometre (560-mile) border with Syria in a bid to stem the flow of militants.

The ****** comes at a time of heightened ******** between Turkey’s security forces and militants linked to the outlawed Kurdistan Workers’ Party, or PKK, in the country’s mostly-Kurdish southeast.

The country is also dealing with more than 2 million Syrian refugees and a wave of migrants from Syria and other countries pouring across Turkey to Europe.

****** sealed the area, barring people from approaching in case of a second *********, and a ****** helicopter hovered overhead.

The Sultanahmet neighbourhood is Istanbul’s main sightseeing area and includes the Topkapi Palace and the former Byzantine ****** of Haghia Sophia, now a museum.

Erdem Koroglu, who was working at a nearby office, told NTV television he saw several people on the ground following the *****.

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

******* Prime Minister Ahmet Davutoglu immediately convened a security meeting with the country’s interior minister and other officials.

As with previous *******, authorities imposed a news blackout, barring media from showing images of the **** or ******* or reporting any details of the *************.

Turkey suffered two major ******* ******* last year, both blamed on the Islamic State group.

More than 30 people were ****** in a ******* ****** in the town of Suruc, near Turkey’s border with Syria, in July.

Two ******* bombs exploded in October outside Ankara’s main train station as people gathered for a peace rally, ******* more than 100 in Turkey’s deadliest-ever ******. The prosecutor’s office said that ****** was carried out by a local Islamic State cell.

Last month, ******* authorities arrested two suspected Islamic State militants they said were planning ******* ******** during New Year’s celebrations in the capital Ankara.