DIYARBAKIR, Turkey - Eight Turkish soldiers were killed in a bomb attack on their vehicle by Kurdish militants in southeast Turkey on Wednesday, the military said, intensifying conflict after the breakdown of a two-year ceasefire last month.

Kurdistan Workers Party (PKK) militants planted explosives on a highway in the province of Siirt and detonated them around 1110 GMT, the general staff said in a statement, as security forces clashed with the PKK across the mainly Kurdish southeast. Security sources said PKK fighters had killed four Turkish soldiers in clashes in Diyarbakir province since Tuesday as a peace process launched by the state. Police detained four mayors from an affiliate party of the HDP in two districts of Diyarbakir over recent statements declaring autonomy from Ankara, the party said.

The conflict comes amid heightened political uncertainty in Turkey, which appears to be heading for a snap election after the collapse of coalition talks. The PKK, designated a terrorist group by Turkey, the United States and European Union, launched its insurgency against the state in 1984 and more than 40,000 people have been killed in the conflict.