Two explosions at a peace rally in the Turkish capital, Ankara, have killed at least 86 people and injured 186, according to officials.
TV footage shows scenes of panic and people lying on the ground covered in blood, amid protest banners.
The blasts took place near the city’s central train station as people gathered for a march organised by leftist groups.
Turkey’s president condemned the attacks as “terrorist acts”.
Recep Tayyip Erdogan denounced what he called “this loathsome attack that targeted our unity and our togetherness”.
Government officials are investigating reports that a suicide bomber was behind at least one of the explosions.
The pro-Kurdish HDP party was among those attending the rally, which was demanding an end to the violence between the Kurdish separatist PKK militants and the Turkish government.
The party said in a statement that it believes its members were the main target of the bombings.
The leader of the HDP has blamed the state for the attack, which he called “a huge massacre”, and cancelled all election rallies.
Turkey is holding a re-run of June’s inconclusive parliamentary elections on 1 November.
Later on Saturday, the PKK called on its fighters to halt its guerrilla activities in Turkey unless attacked first.
A statement from an umbrella group that includes the PKK said its forces would “not engage in any kind of activity apart from preserving its current position and make no attempts to hinder or harm the exercise of a fair and equal election”.
The HDP was among those joining Saturday’s rally for “peace and democracy”, called for by the confederation of trades unions, which was due to start at 12:00 local time.
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, before the first blast.
The HDP tweeted that police “attacked” people carrying the injured away.
Opposition MP, Musa Cam, tweeted a photo of a ball bearing he says he found at the scene.