Turkey is beginning three days of mourning after two blasts at a peace rally in the capital, Ankara, killed at least 95 people on Saturday, the deadliest ever such attack in Turkey.
The attack left 245 people injured, with 48 of them in a serious condition.
TV footage showed scenes of panic and people lying on the ground covered in blood, amid protest banners.
The government called the blasts a "terrorist act" and angrily rejected allegations that it was to blame.
Prime Minister Ahmet Davutoglu said there was evidence that two suicide bombers had carried out the attack, which comes three weeks before a re-run of June's inconclusive parliamentary elections.
The blasts took place near the city's central train station as people gathered for a march organised by leftist groups demanding an end to the violence between the Kurdish separatist PKK militants and the Turkish government.
The two explosions happened shortly after 10:00 as crowds gathered ahead of the rally. Amateur video footage showed a group of young people holding hands and singing, as the first blast hits.
No group has said it carried out the attack, but Mr Davutoglu suggested that Kurdish rebels or the Islamic State (IS) group were to blame.
Terrorism experts have said the attack is similar to one that was carried out in Suruc in southern Turkey by IS in July in which 30 people died, says the BBC's Selin Girit in Ankara.
After the ceasefire between the PKK and the Turkish state broke down in July, Turkey has spiralled into tit-for-tat attacks between the two sides, and tension between Kurds and Turkish nationalists has soared.
Amidst the frenzy of a repeat election in November, it was expected that something dangerous was imminent.
The pro-Kurdish HDP party has blamed the state. That is undoubtedly a reference to the so-called "deep state" often talked about here: a shady mix of nationalist forces either colluding with or supporting the government in power.
The West's vital ally in the Middle East is now facing a perfect storm: deep political polarisation, the bubble of economic success on the brink of bursting, a resumption of violence with the PKK, the threat from Islamic State, and two million Syrian refugees and counting.
The tragedy in Ankara is a sign of the dark times Turkey is now facing.
However, the leader of the pro-Kurdish HDP party, whose members was among those attending the rally, has blamed the state and cancelled all election rallies.
An HDP rally in the city of Diyarbakir was bombed in June, ahead of general elections in which the party entered parliament for the first time.
The party has previously blamed the government for colluding in attacks on Kurdish activists, which the government denies.
Cemalettin Hasimi, director of press and information at the prime minister's office, told the BBC that such allegations were "a disgrace, unacceptable".
No group has yet said it carried out the attack
A ceasefire between the Kurdish militant group the PKK and Turkey's government broke down after the attack in Suruc, with the PKK accusing the security forces of collaborating with IS.
This led to an increase in attacks from both sides over the summer.
On Saturday, the PKK called on its fighters to halt its guerrilla activities in Turkey except in cases of self-defence. A statement from an umbrella group that includes the PKK said its forces would "make no attempts to hinder or harm the exercise of a fair and equal election".