Explosion rocks central Istanbul square, some casualties - Dogan news agency

A police officer secures the area after an explosion near the Ottoman-era Sultanahmet mosque, known as the Blue mosque in Istanbul, Turkey January 12, 2016. REUTERS/Osman Orsal

ISTANBUL (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 centre 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.