The Turkish government has made increasingly confident declarations of responsibility for the deadly Ankara car bomb attack this weekend, which is now said to have killed at least 37 people.

The perpetrators of the attack have been described by Turkish officials as a 22-year-old female militant, originally from the city of Kars on the Armenian border, who joined the Kurdish PKK separatist party in 2013. She was assisted by a Turkish man with “PKK links,” according to the Turkish government.

Reuters reports a Turkish police source said the severed hand of the female bomber was found 300 meters away from the blast site, a grisly testimony to the power of the bomb.

According to Sky News, the bombing was carried out using a BMW automobile that was “packed with nails and pellets, to cause maximum damage.”

Turkish police reportedly identified the bombers by tracing the car back to the southeastern town of Sanliurfa, where the vehicle was purchased. Four people were subsequently arrested in Sanliurfa in connection with the plot, while another 36 suspected Kurdish militants were arrested in the southern city of Adana, plus 15 more in Istanbul.

Turkish fighter jets attacked targets described as “arms depots and shelters of the PKK in the Iraqi mountainous areas of Qandil and Gara on Monday” in a Turkish military report related by Sky News. The BBC says eleven warplanes carried out strikes against 18 targets.

Turkish security forces are also preparing for major operations in two Kurdish towns, Yuksekova and Nusaybin, located near the borders with Iran and Syria respectively. Both towns have been placed under open-ended 24-hour curfews. Another curfew is due to begin soon in the city of Sirnak.

Deutsche Welle notes that security operations in Kurdish population centers have been controversial, with the government unwilling to discuss the number of military or civilian casualties at length. “The operations have laid waste to several Kurdish towns, making them look like war-torn Syria,” DW observes.

Critics in the mainstream pro-Kurdish party of Turkey, the HDP, are already saying the round-the-clock curfews imposed on Yuksekova and Nusaybin amount to the Turkish military laying siege to the towns. Deutsche Welle reports some residents fleeing the towns in advance of the curfew.

There has not yet been a formal claim of responsibility for the Ankara bombing.