An explosion in the heart of Istanbul's historic Sultanahmet tourist district killed 10 people and wounded 15 on Tuesday, an attack that Turkey's prime minister blamed on the Islamic State in Iraq and the Levant (ISIL).
Turkish Prime Minister Ahmet Davutoglu said the sole perpetrator belonged to ISIL. Davutoglu pledged to battle the armed group until it no longer "remains a threat" to Turkey or the world.
"Turkey won't backtrack in its struggle against Daesh by even one step," Davutoglu said, referring to ISIL by an Arabic acronym. "This terror organization, the assailants and all of their connections will be found and they will receive the punishments they deserve."
Davutoglu described the attacker as a "foreign national." Deputy Prime Minister Numan Kurtulmus had previously said the perpetrator was born in 1988 and was a Syrian national, but the private Dogan news agency claimed the bomber was Saudi-born.
Eight of the 10 people killed were German tourists, Turkish officials said. Turkey's state-run news agency said Davutoglu held a telephone conversation with German chancellor Angela Merkel to express his condolences. Davutoglu said the death toll of 10 did not include the suicide bomber.
Merkel offered her thoughts for the victims of the Istanbul bombing and condolences for their families, and promised Germany would continue to fight against terror.
"Today Istanbul was the target, before Paris, Copenhagen, Tunis, and so many other areas," she told reporters in Berlin. "International terror changes the places of its attacks but its goal is always the same — it is our free life in free society. The terrorists are the enemies of all free people, indeed, the enemies of all humanity, whether in Syria or Turkey, in France or Germany."
In the bombing's aftermath, several bodies could be seen on the ground in the Sultanahmet square, a bustling area of Turkey's most populous city close to the popular Blue Mosque and Hagia Sophia tourist sites.
Police sealed the area, barring people from approaching in case of a second explosion, and a police helicopter hovered overhead. Among the wounded were German, Norwegian, Peruvian and South Korean nationals, reports said.
The attack at the heart of one of the world's most visited cities comes as Turkey battles Kurdish fighters in its southeast and ISIL insurgents just across its southern borders in Syria and Iraq.
There was no immediate claim of responsibility for the attack. The Istanbul governor's office said the authorities were investigating the type of explosive used.
"We heard a loud sound and I looked at the sky to see if it was raining because I thought it was thunder but the sky was clear," said Kuwaiti tourist Farah Zamani, 24, who was shopping at one of the covered bazaars with her father and sister.
"The explosion was very loud. We shook a lot. We ran out and saw body parts," one woman who works at a nearby antiques store told Reuters, declining to give her name.
Davutoglu held an emergency meeting in Ankara with the interior minister and security chiefs. Davutoglu's office imposed a broadcasting ban on the blast, invoking a law which allows for such steps when there is the supposed potential for serious harm to national security or public order.
Since ISIL's rapid rise over the last two years, Turkey has become a target for the group, with two major bombings last year in the town of Suruc near the Syrian border and in the capital, Ankara. The latter killed more than 100 people.
Just over a year ago, a female suicide bomber blew herself up at a police station for tourists off the same square as Tuesday's attack, killing one officer and wounding another. That attack was initially claimed by a far-left group, but officials later said it had been perpetrated by a woman with suspected links to ISIL.
Ankara is in the midst of a wide crackdown on groups it considers "terrorists," including ISIL and the leftist Kurdistan Workers Party (PKK) insurgent group. Violence has escalated in the mainly Kurdish southeast since a two-year ceasefire collapsed in July between the state and the PKK, which has been fighting for three decades for Kurdish autonomy.
But the PKK has generally avoided attacking civilian targets in urban centers outside the southeast in recent years, leading most to suspect that ISIL could be behind Tuesday's attack.
If that is the case, "it would reflect a shift in the group’s strategy and herald a broader campaign against Turkey," said Firas Abi Ali, a senior analyst at IHS Country Risk, a consultancy based in London. Whereas ISIL fighters once enjoyed relatively free passage from Turkey into Syria, where Ankara initially hoped groups like ISIL would prove useful in fighting the Syrian government of Bashar al-Assad, Turkey has shifted course by increasing cooperation with the U.S.-led anti-ISIL campaign across Syria and Iraq.
Noting that ISIL propaganda has increasingly threatened Turkey, Abi Ali said ISIL's territorial losses in Iraq and Syria "may well have led the group to assess that it needs to expand its influence and capability in Turkey before it can reverse these losses. If so, this is a high-risk endeavor that will likely provoke a significant backlash by the Turkish government."
Al Jazeera and wire services