Thousands have mourned the 95 victims of Turkey's deadliest attack in years as state inspectors tried to identify who sent suicide bombers to a rally promoting peace with Kurdish rebels in the country.
The government said Kurdish rebels or Islamic State (IS) militants were likely responsible, while mourners accused President Recep Tayyip Erdogan of fomenting violence to gain votes for the ruling party.
No-one has claimed responsibility, but the attack bears similarities to a suicide bombing the government blames on IS, which killed 33 Turkish and Kurdish peace activists near a town bordering Syria in July.
Police detained 14 suspected Islamic State members on Sunday in the central Turkish city of Konya, but it was not clear if they were related.
Some Turkish media declared that peace itself was under attack. The bombers struck hours before Kurdish rebels battling Turkish security forces followed through with plans to declare a unilateral ceasefire, to reduce tensions leading up to November 1 elections.
Turkey's government rejected the declaration, saying the rebels must lay down arms for good and leave the country.
While no one group has been ruled out in the bombings, government opponents blamed security forces for failing to protect the peace rally.
Selahattin Demirtas, co-chairman of the pro-Kurdish People's Democracy Party, said: "The state which gets information about the bird that flies and every flap of its wing, was not able to prevent a massacre in the heart of Ankara.
Mr Demirtas said government officials should apologise to the people and resign. Some mourners chanted: "Murderer Erdogan!" Thousands also demonstrated in Istanbul on Saturday, blaming the government.
Mr Erdogan is hoping the ruling party regains its political majority, and critics accuse him of intensifying attacks on Kurds to rally nationalist votes. They worry the bombings could entice rogue Kurdish forces to attack, persuading Turks to seek security over peace.
IS, which is fighting Syrian Kurdish forces allied to Turkey's Kurdish rebels, could benefit the most from this, since a continued military offensive within Turkey would take pressure off the extremist group in Syria.
The Syrian government also has an interest in destabilising Turkey, which has made no secret of its desire to see President Bashar Assad ousted.
Regardless of who may have planned the attack, it showed how deeply Turkey is being drawn into the chaos in Syria, with which it shares a 560 mile-long border.
Turkey already hosts some 2.2 million refugees from Syria - more than any other nation - and extremists use Turkish territory to enter or exit the fray, increasing the threat of violence.
Turkey's skies also are vulnerable. Russia reportedly violated Turkish airspace last week while bombing anti-Assad rebels in Syria, and on Sunday, Turkey's military said Syrian jets and surface-to-air missile systems locked radars on three of Turkish F-16 jets patrolling the border.
Kemal Kilicdaroglu, leader of Turkey's pro-secular opposition party, blamed Turkey's support of opposition groups in Syria for the violence.
"That policy has brought terror to our country," Mr Kilicdaroglu said. "Turkey needs to rapidly get out of the Middle Eastern quagmire."
Turkey agreed recently to more actively support the US-led battle against the Islamic State group, opening its bases to US aircraft launching air strikes on the extremist group in Syria and carrying out a limited number of strikes on the group itself.
Relations between Kurds and Turks are already tense. Hundreds have died in Turkey in the last few months as a 2012 peace process was shattered.
Electoral gains by the People's Democracy Party in June deprived the ruling party, which Mr Erdogan founded, of its parliamentary majority after a decade of single-party rule. The new election was called after the ruling party failed to strike a coalition deal.
Mr Erdogan is seeking to extend the executive powers of his presidency, and while he denies it, opponents believe he has deliberately reignited the conflict with the Kurdistan Workers' Party, or PKK, to shore up his party's support. Mr Erdogan has asserted that Kurdish rebels are a bigger threat to Turkey than IS.
Opinion polls indicate, meanwhile, that the ruling party is unlikely to regain a majority, again forcing it to build a governing coalition. Just how Saturday's bombings will affect all this remains to be seen.
On Sunday, police fired tear gas and scuffled with the mourners trying to reach the site of the explosions to lay down carnations in respect of the dead. A group of about 70 mourners was eventually allowed to enter the cordoned off area.
The government announced that it had appointed two civil and two police chief inspectors to investigate the attack. Yeni Safak, a newspaper close to the government, said investigators had determined that one of the bombers was a male, aged about 25 or 30. Mr Kilicdaroglu said the attacks were carried out by two male bombers.
Turkey's military on Sunday said it had carried out a new round of cross-border airstrikes against PKK shelters and positions in the regions of Zap and Metina, in northern Iraq.