Images from the scene on Tuesday showed several bloody corpses lying on the ground close to the iconic Ottoman-era Blue Mosque in Sultanahmet, a district home to Istanbul’s biggest concentration of historic monuments.
Turkey has been hit by a string of deadly attacks this year, but Tuesday’s bombing was the first time in recent memory tourists had been targeted in the heart of the city.
German Chancellor Angela Merkel said at least eight Germans were amongst the dead and warned its nationals to keep away from public places and tourist attractions, although a Turkish official said nine had been killed.
UN chief Ban Ki-moon condemned the attack on Istanbul, a city of 14 million and Turkey’s commercial hub, as “despicable”.
“The terrorists are the enemies of all free people, they are enemies of humanity, be it in Syria, Turkey or France or Germany,” Merkel said, stressing that Berlin would fight terror “with determination”.
Peru confirmed one of its nationals had died in the attack, while Oslo said a Norwegian was one of 15 people wounded in the blast. Turkish media reports said German and Peruvian tourists were also among those hurt.
Turkish President Recep Tayyip Erdogan said the attack was carried out “by a suicide bomber of Syrian origin”, while Prime Minister Ahmet Davutoglu said the man belonged to the Islamic State extremist group.
Officials said he was a Syrian born in 1988.
Turkey has been on high alert after a series of attacks blamed on the Islamic State jihadist group, including a double suicide bombing in October in Ankara that killed more than 100 people.
‘Ball of fire’
The explosion occurred in the mid-morning by the Obelisk of Theodosius, a monument from ancient Egypt that was re-erected by the Roman Emperor Theodosius and stands just outside the famous Blue Mosque.
Police threw up a tight security cordon around the area as helicopters hovered overhead, and crowds of worried locals and tourists clamoured to find out what had happened, an AFP correspondent said.
“The explosion was so loud, the ground shook. There was a very heavy smell that burned my nose,” a German tourist named Caroline told AFP.
“I heard a very loud blast, then came the screams,” added a Turkish man who did not want to be identified, adding: “Then I saw a ball of fire, and started to run away.”
The authorities imposed a broadcast ban on reporting of the attack, prompting television channels to halt live coverage from the scene.
Berlin travel agency Lebenslust Touristik said several of the Germans killed in the blast were on one of its tours when the attack happened, warning the number of injured could rise.
“It is feared that more members of the group have been hurt,” it said in a statement, adding that 33 people were in Istanbul with the operator at the time of the attack.