Kurdish rebels say they will resume fighting against the Turkish army, ending a unilateral ceasefire.
The PKK had announced a truce ahead of Turkey's parliamentary elections, which were won by President Recep Tayyip Erdogan's AK Party on Sunday.
The PKK says its fighters will now be "resuming activities" in the country's predominantly Kurdish south-east.
President Erdogan vowed to "liquidate" the PKK on Wednesday. A long-running peace process collapsed in July.
"The unilateral halt to hostilities has come to an end with the AKP's war policy and the latest attacks," the Kurdistan Workers' Party (PKK) said in a statement to a local news agency.
A pro-PKK website said more information would be published soon "explaining the reasons behind the decision to resume armed activities against the Turkish occupation army".
The ceasefire - announced on 10 October - was intended to allow a "fair and just election", but the Turkish government dismissed it as an electoral tactic.
In his first major speech since the AKP's win, the president on Wednesday vowed to continue operations against the group, which Turkey - along with the United States and the European Union - deems a terrorist group.
Two soldiers and 15 PKK militants were killed in fighting in the Hakkari province in the south east on Wednesday, just a day after Turkey carried out air strikes in the area.