Bombs killed 14 people and wounded 140 in Istanbul late on Sunday, just hours ahead of a court case over banning the ruling party that has plunged Turkey into political turmoil.
Officials said one loud blast brought people into the streets of a busy shopping area, then a larger bomb hidden in a rubbish bin exploded a few minutes and a few metres away, tearing through the crowds.
"This is a terror attack," city governor Muammer Guler told reporters at the scene, in a pedestrianised street where families gather in the evenings to dine, sip tea and stroll.
Television showed ambulances taking away the wounded in the Gungoren district of Turkey's biggest city, near the main airport. Among the rubble and glass of broken shop windows, men carried away the wounded and children cried.
"First a percussion bomb exploded and then a bomb in a garbage container," Deputy Prime Minister Hayati Yazici told reporters.
One witness said: "Tens of people were scattered around. People's heads, arms, were flying in the air."
Turkish media put the toll at 14 dead and 140 wounded. Earlier, officials confirmed 13 dead and more than 100 wounded.
"I condemn those who carried out this bombing, which shows us terrorism's inhumane desire for cruelty and violence without discriminating between men and women, young, old and children," President Abdullah Gul said in a statement.
Kurdish separatists, far-left groups and Islamists have all carried out bombings in Istanbul in the past.
Turkey has been plunged into political and economic uncertainty by the court case over banning the ruling party that begins on Monday.
The Constitutional Court will deliberate on whether the AK Party has engaged in Islamist activities and should be closed.
Police have also been widening an investigation into a suspected ultra-nationalist group accused of seeking to overthrow the government. So far 86 people have been arrested.
Turkey's military has been active in a campaign against Kurdish separatists in the southeast, saying earlier on Sunday its fighter jets had hit 12 rebel targets.
Governor Guler said the "heinous attack" in Istanbul was not a suicide bombing. The city straddles Europe and Asia. Gungoren is on the European side.
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