At least 95 people were killed when two suspected suicide bombers struck a rally of pro-Kurdish and labour activists outside Ankara's main train station just weeks before elections, in the worst attack of its kind on Turkish soil.
Bodies covered by flags and banners, including those of the pro-Kurdish opposition Peoples' Democratic Party (HDP), lay scattered on the road among bloodstains and body parts. The HDP blamed the government which, it said, had blood on its hands.
Footage screened by broadcaster CNN Turk showed a line of young men and women holding hands and dancing, and then flinching as a large explosion flashed behind them, engulfing people carrying HDP and leftist party banners.
"Like other terror attacks, the one at the Ankara train station targets our unity, togetherness, brotherhood and future," said President Tayyip Erdogan, who has vowed to crush a Kurdish militant insurgency since the collapse of a ceasefire and resumption of intense violence in July.
Witnesses said the two explosions happened seconds apart shortly after 10 a.m. as crowds, including HDP activists, leftists, labour unions and other civic groups, gathered for a planned march to protest over the deaths of hundreds since conflict resumed between security forces and the Kurdistan Workers Party (PKK) in the mainly Kurdish southeast.
"I heard one big explosion first and tried to cover myself as the windows broke. Right away there was the second one," said Serdar, 37, who was working at a newspaper stand in the train station. "There was shouting and crying and I stayed under the newspapers for a while. I could smell burnt flesh."
There were no claims of responsibility for the attack, which comes as external threats mount for NATO member Turkey with increased fighting across its border with Syria and incursions by Russian warplanes on its air space over the last week.
But Prime Minister Ahmet Davutoglu, exposing a mosaic of domestic political perils, said Islamic State, Kurdish or far-leftist militants could have carried out the bombing. He said there were strong signs two suicide bombers were responsible.
HDP leader Selahattin Demirtas blamed the government in blunt terms. He said the attack was part of the same campaign as the bombing of an HDP rally in the southeastern city of Diyarbakir on the eve of June elections and a suicide bombing blamed on Islamic State in Suruc near the Syrian border in July, which killed 33 mostly young pro-Kurdish activists.
"The government's right and chance to hum and haw has long expired. You are murderers. Your hand is bloody. Blood has splattered from your face, your mouth to your nails and all over you. You are the biggest supporters of terror," he told reporters in comments broadcast on the internet.
The HDP argues that Erdogan seeks to undermine its support and increase backing for his AK Party in elections due on Nov. 1 by associating it with PKK violence and factional infighting, a link the party denies strongly.
Sources in Erdogan's office said U.S. President Barack Obama called the president on Saturday evening to convey his condolences, condemn the attack and stress that Washington would continue to stand beside Turkey in its fight against terror.