Brussels - NATO's top official on Monday condemned the night's double bomb attack in Istanbul which left at least 16 people dead and over 150 injured.

"I condemn in the strongest terms the bombings that occurred in Istanbul yesterday (Sunday) evening. These appalling terrorist attacks targeted innocent civilians in a deliberate and brutal way," NATO Secretary General Jaap de Hoop Scheffer said in a statement.

"On behalf of the (NATO) allies, I express my condolences to the families of those who lost their lives, and my sympathies to those injured in the blasts. NATO will continue to stand firmly in solidarity with the Turkish people in the fight against terrorism," he said.

The double bombing on Sunday evening struck a crowded pedestrian street in the Istanbul suburb of Gungoren. Police on Monday morning were searching for clues as to the perpetrators, with Kurdish separatists and Islamist extremists among the suspects.

Turkey is a member of NATO and is home to the alliance's top counter-terrorism research centre. (dpa)