A suspected member of the Islamic State (IS) group has killed 10 people, at least nine of them German tourists, in a suicide bomb attack in the Turkish city of Istanbul, officials say.
They say the Syrian national carried out the attack in the Sultanahmet district, near the famous Blue Mosque.
Fifteen people were wounded, many of them also German.
President Recep Tayyip Erdogan said Turkey was the “top target for all terrorist groups in the region”.
His country, he added, was “fighting against all of them equally”.
According to BBC, Turkish Prime Minister Ahmet Davutoglu telephoned German Chancellor Angela Merkel to offer his condolences, the Anadolu news agency quoted his office as saying.
Mr Davutoglu later said: “We have determined that the perpetrator of the attack is a foreigner who is a member of Daesh (IS).”
He vowed to find and punish those linked to the bomber and pledged to continue the fight against IS militants.
Turkey’s Deputy PM Numan Kurtulmus said earlier: “It has been identified that the suicide bomber is Syrian and his connections are being investigated.”
The suspect was said to have been born in 1988 and was identified from body parts.
Mr Kurtulmus said the suspect was not on Turkey’s militant watch-list and was believed to have recently crossed into Turkey from Syria.
Eyewitness Murat Manaz said: “It was a suicide bomb. I went there and saw it and came back to the hotel. There was chaos. Everybody was running somewhere.
“Policemen did not see this coming. They were distressed but at the same time they were trying to evacuate the area because they said there was a possibility that a second bomb could go off.”
The authorities are investigating the type of explosive used, the Istanbul governor’s office said.
Mrs Merkel had earlier expressed “serious concern” about the casualties, saying a German tourist group had been affected.
She added: “Today Istanbul was hit; Paris has been hit, Tunisia has been hit, Ankara has been hit before. International terrorism is once again showing its cruel and inhuman face today.”
Germany’s foreign ministry has on its website (in German) urged German tourists in Istanbul to avoid large crowds and tourist attractions and warned that further violent clashes and “terrorist attacks” were expected across Turkey.
Norway’s foreign ministry said a Norwegian man was receiving treatment in hospital.
Turkey last year took a more active role against IS in Syria, carrying out air strikes and allowing US warplanes to use its Incirlik base for missions.
What is the security situation in Turkey?
Turkey faces myriad security threats and establishing which group is behind this latest attack will be a matter of urgency. The Islamic State group has been blamed for three bombings in Turkey in the past year, including an attack in Ankara that killed more than 100 people. Violence has also soared between Turkish security forces and PKK militants, battling for more autonomy for the Kurds, after a ceasefire agreement broke down in July. A PKK offshoot, the TAK, fired a mortar at Istanbul airport last month. Far left groups are also active in Turkey, and a female suicide bomber attacked a police station in Istanbul’s Sultanahmet district last year.
Who could be behind the latest attack?
President Erdogan has blamed a “suicide bomber of Syrian origin”. The conflict in Syria has not only seen the rise of IS but also strengthened the PKK’s offshoot in Syria, known as the YPG. There was no immediate claim of responsibility, but correspondents point out that IS was similarly silent following previous attacks last year that were widely blamed on the jihadist group.
How is the Turkish government responding?
Last year Turkey agreed to take a more active role in the US-led campaign against IS, carrying out air strikes in Syria. It also allowed US warplanes to strike IS targets from its base in Incirlik and moved to tighten security along its 900km (560 mile) border with Syria. Meanwhile Turkish forces have also been targeting Kurdish militants in northern Iraq. And violence has flared in Turkey’s mainly Kurdish south-east, where the Turkish military says it has killed some 600 PKK militants over the past month, according to Anadolou Agency.