ON SATURDAY morning thousands of pro-peace demonstrators began gathering in Ankara, Turkey's capital, to call for an end to the cycle of violence that has engulfed the country since late July. As the demonstrators were disembarking in front of the city's main train station, two explosions tore through the crowd. By mid-afternoon the toll of casualties stood at 86 killed and 186 injured, according to Turkey's health minister, Mehmet Muezzinoglu. A parliamentary candidate for the pro-Kurdish People's Democratic Party (HDP) was among the dead. It was the worst terror attack in Turkish history. With the government ramping up a military campaign against Kurdish separatists and parliamentary elections drawing near, the country risks descending into a bloodbath.

No one has yet claimed responsibility. But the attack bears a strong similarity to the bombing, attributed to an Islamist militant, which caused the death of 33 young activists in the town of Suruç near the Syrian border on July 20th. That attack led rapidly to the collapse of the fragile two-year peace process between the Turkish authorities and the separatist Kurdistan Workers’ Party (PKK): the PKK responded by attacking Turkish soldiers and police, and the Turkish authorities announced the resumption of their military operations.

Since then the violence has spread rapidly. Dozens of Turkish security personnel, PKK fighters and innocent civilians have been killed. As the clashes moved to urban centres, authorities imposed curfews on several towns in the south-east. But ethnic violence between Turks and Kurds has since flared up all across the country. Hundreds of people have been arrested. Turkish government officials have begun describing the HDP, the moderate Kurdish party which pressed for the peace negotiations, as a terrorist organisation. Nationalist mobs have attacked dozens of HDP offices across the country; several have been burned.

The descent into the maelstrom has been quick and surprising. Until last year Turkey, despite the strains of the civil war in neighbouring Syria, was stable and peaceful, and seemed to be on its way to resolving the long-running Kurdish conflict. That stability began to unravel after parliamentary elections on June 7th, when the Justice and Development party (AK), which has dominated Turkish politics since 2002, lost its majority as the HDP snatched key seats in Turkey’s south-east. Recep Tayyip Erdogan, Turkey’s strong-man president and a co-founder of AK, was determined to undo that result. After the AK's desultory efforts to form a coalition government failed, Mr Erdogan called for new elections on November 1st. Mr Erdogan and the AK are widely believed to have escalated the war against the Kurds in order to inflame nationalist feelings and drive down the HDP's share of the vote.