TURKEY(ISTANBUL) - UPDATE -A suicide bomber affiliated with the Islamic State group detonated a bomb in a historic district of Istanbul popular with tourists Tuesday morning, killing at least 10 people - nine of them German tourists - and wounding 15 others, Turkish officials said, Turkish Prime Minister Ahmet Davutoglu said the bomber who carried out the attack in Istanbul's Sultanahmet district was a member of IS and pledged to battle the militant group until it no longer "remains a threat" to Turkey or the world. 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."Turkey won't backtrack in its struggle against Daesh by even one step," Davutoglu said, referring to IS by its Arabic acronym. "This terror organization, the assailants and all of their connections will be found and they will receive the punishments they deserve." Turkey's state-run news agency said Davutoglu held a telephone conversation with German chancellor Angela Merkel to express his condolences. A senior government official confirmed that most of the victims were German. Merkel had earlier said they were part of a German travel group.