A suicide bombing on Tuesday in the tourist heart of Istanbul left 10 dead, with officials saying the attacker was a man with links to Syria.
Deputy Prime Minister Numan confirmed foreigners were among the dead, but did not specify nationalities.
Mr. Numan identified the suspect as a Syrian born in 1988.
He said added that of the 15 people injured, two were in serious condition.
Meanwhile a source from the office of the Turkish Prime Minister said on condition of anonymity that nine Germans were among the dead in the Sultanahmet area.
He said the large blast, which could be heard several kilometres away, took place at around 10:15 am (0815 GMT) in Sultanahmet, home to the Hagia Sophia museum and the Blue Mosque, both major tourist attractions on the European side of the metropolis.
The German Foreign Office said it was in touch with the Turkish authorities and was urging citizens to avoid crowded areas in Istanbul.
Speaking in Ankara, President Recep Tayyip Erdogan condemned the “terrorist” attack and said a person of Syrian origin was the perpetrator, according to initial assessments.
No group has claimed responsibility for the attack, which comes amid rising violence in Turkey.
The authorities blamed three major suicide attacks last year on the Islamic State extremist group, which controls territory in neighbouring Syria and Iraq.
The group has never claimed an attack in Turkey. There is also ongoing fighting with Kurdish militants.
A large group of police and emergency workers were at the scene after police cordoned off the area near the blast.
The government has also imposed a temporary broadcast ban in the wake of the explosion.
Turkey which borders both Iraq and Syria, two nations in the throes of civil wars has been facing increasing unrest during the past year.
The largest blast in the country’s history took place in October, in Ankara.
Two suicide bombers blew themselves up near a train station during a pro-Kurdish peace rally, killing 100 people.
Islamic State militants were blamed for that attack, as well as for another suicide blast in July in the south of the country, which left more than 30 people dead. The group never claimed responsibility.
Turkey stepped up its fight against Islamic State last year, after a period in which it was criticized for being slow to tackle the threat from the extremist group.
The last major terrorist attack in the city took place in 2003, when suspected al-Qaeda-affiliated militants detonated four truck bombs in two days, killing at least 57 people.
The attacks targeted Jewish synagogues, a bank and the British consulate.