At least 13 people have been killed and 70 wounded after two bombs exploded in a busy shopping district in Istanbul.
'It is certain that this is a terror attack,' governor Muammer Guler told reporters at the scene.
TV showed ambulances carrying badly wounded people to hospital after the explosions at two different sites in the Gungoren district of Turkey's biggest city.
The victims were killed by the second explosion after a small blast in a telephone kiosk brought people out onto the street.
The governor said the bombs were in rubbish bins and that it was not a suicide bombing.
'The blasts occurred in a very busy district and this raised the casualties. 13 citizens lost their lives in this heinous attack,' he said.
One witness said: 'Tens of people were scattered around. People's heads, arms, were flying in the air.'
'We received nearly 30 very heavily wounded people,' said Abdullah Toker, a manager at Gungoren Kolon Hospital.
Several groups, including Kurdish separatists, far-left groups and Islamists, have carried out bomb attacks in Istanbul in the past.
