ISTANBUL, Jan 12 (Reuters) - A suicide bomber thought to have crossed recently from Syria killed at least 10 people, most of them German tourists, in Istanbul's historic heart on Tuesday, in an attack Prime Minister Ahmet Davutoglu blamed on Islamic State.

All of those killed in Sultanahmet square, near the Blue Mosque and Hagia Sophia - major tourist sites in the center of one of the world's most visited cities - were foreigners, Davutoglu said. A senior Turkish official said nine were German, while Peru's foreign ministry said a Peruvian man also died.

Deputy Prime Minister Numan Kurtulmus said the bomber was believed to have recently entered Turkey from Syria but was not on Turkey's watch list of suspected militants. He said earlier that the bomber had been identified from body parts at the scene and was thought to be a Syrian born in 1988.

A Turkish government official told The WorldPost that the Ministry of Interior could not yet confirm nor deny reports the bomber was identified as a Saudi man named Nabil Fadli.

Davutoglu said he had spoken by phone with German Chancellor Angela Merkel to offer condolences and vowed Turkey's fight against Islamic State, at home and as part of the U.S.-led coalition, would continue.

"Until we wipe out Daesh, Turkey will continue its fight at home and with coalition forces," he said in comments broadcast live on television, using an Arabic name for Islamic State. He vowed to hunt down and punish those linked to the bomber.