Mazar-e Sharif, Afghanistan - German Foreign Minister Frank-Walter Steinmeier on Monday condemned the double bomb blasts that hit a crowded street in Istanbul as "a blind act of terrorism."

Speaking from Afghanistan, where he is visiting German forces and development workers, Steinmeier said Germany would stand by Turkey.

He called for those responsible for Sunday night's attack to be brought to account.

The bombs hit the Istanbul suburb of Gungoren. Fifteen people were reported killed and about 150 injured. (dpa)