At least 95 people were killed in Ankara Saturday when bombs set off by two suspected suicide attackers ripped through a crowd of leftist and pro-Kurdish activists at an anti-government peace rally, in the deadliest attack in the history of modern Turkey.
The twin blasts, near Ankara's main train station, ratcheted up tensions ahead of Turkey's November 1 snap elections which were already soaring amid the government's offensive on Kurdish militants.
Bodies of slain demonstrators were seen strewn across the ground after the explosions, with the banners they had been holding for the "Work, Peace and Democracy" rally lying next to them.
The attack also left 246 wounded, 48 of whom are in intensive care, according to an updated toll announced by Prime Minister Ahmet Davutoglu's office.
President Recep Tayyip Erdogan denounced the "heinous attack", saying it was aimed at "our unity and our country's peace."
Declaring three days of mourning, Davutoglu said there were "strong signs" the attack were carried out by two suicide bombers.
There were scenes of chaos after the blasts, as ambulances raced to get to the wounded and police cordoned off the blood-stained area around the train station.
"We heard one huge blast and then one smaller explosion and then there was a great movement and panic. Then we saw corpses around the station," said Ahmet Onen.
"A demonstration that was to promote peace has turned into a massacre, I don't understand this," he said, sobbing.
Davutoglu said no one had claimed responsibility for the bombings but that groups including the Islamic State (IS) jihadists, the Kurdistan Workers' Party (PKK) and the far-left Revolutionary People's Liberation Party-Front (DHKP-C) were capable of carrying out such an attack.
Amateur footage filmed moments before the blasts and broadcast by NTV television showed smiling activists holding hands and dancing before suddenly falling to the ground as a huge explosion went off behind them.
Reports said hundreds of people in Ankara rushed to hospitals to donate blood for the victims.
The death toll surpassed that of the May 2013 twin bombings in Reyhanli on the Syrian border that killed over 50 people.
With international concern growing over instability in the key NATO member, EU foreign policy chief Federica Mogherini urged Turkey to "stand united against terrorists."
UN Secretary General Ban Ki-moon said in a statement he "expects the perpetrators of these terrorist acts to be swiftly brought to justice".
French President Francois Hollande condemned the "odious terrorist attack" while Russian President Vladimir Putin passed his condolences to Erdogan.
US National Security Council spokesman Ned Price said "the fact that this attack occurred ahead of a planned rally for peace underscores the depravity of those behind it."
Turkey's pro-Kurdish Peoples' Democratic Party (HDP) had been one of the groups that called for the peace rally.
"We are faced with a huge massacre. A barbaric attack has been committed," said HDP leader Selahattin Demirtas, blaming a "mafia state" and a "state mentality which acts like a serial killer" for the attack.
Among those killed was Kubra Meltem Mollaoglu, an HDP member who was standing for parliament in the upcoming polls.
In Istanbul, some 10,000 people marched down the city's main central avenue later on Saturday to denounce the attacks.
Thousands also took to the streets in solidarity in Paris, Strasbourg and Marseille in France, as well as in Zurich in Switzerland.