The PKK is being blamed for a bomb attack in central Turkey which has killed at least 13 people.
Turkey's president Recep Erdogan claims terrorists were behind the explosion which targeted a bus carrying military personnel which also left 55 other people injured.
The blast comes a week after a car bomb attack claimed by Kurdish militants killed 44 people, mainly riot police posted outside a football stadium in Istanbul.
The army said 48 troops were among those wounded in Saturday's "treacherous attack".
The state-run Anadolu Agency said the explosion happened at the entrance to Erciyes University, hitting a public bus which included soldiers among its passengers.
Minister Suleyman Soylu, speaking in Kayseri, said six of the injured were in a critical condition.
Images taken moments after the explosion showed a smoking public bus, still in flames, with its windows blown open and its interior blackened.
There was no immediate claim of responsibility but statements from top officials suggested suspicion was focused on the outlawed Kurdistan Workers' Party, or PKK, which Ankara and the West consider a terrorist organisation.
Kurdish militants have claimed multiple attacks against soldiers and police across Turkey this year in violence that has also caused casualties among civilians.
"Turkey is under a combined attack by terrorist organizations, especially the divisive terrorist organisation," President Recep Tayyip Erdogan said in a statement released by his office Saturday, referring to the PKK.
The Turkish state has fought PKK for decades in a conflict which has claimed tens of thousands of lives. The collapse of a two-and-a-half-year ceasefire in July 2015 set the stage for a violent new chapter and ushered vast security operations in the predominantly Kurdish south-east.
Turkey is also at odds with Western-backed Kurdish factions fighting against the Islamic State in neighbouring Syria and Iraq. Turkey views these groups as extensions of the PKK.
"We know that these attacks we have endured are not unrelated to happenings in Syria and Iraq, or even our economical fluctuations," said Mr Erdogan.
A state of emergency was declared following a botched coup attempt on July 15 and remains in force.
Turkey's prime ministry office imposed a temporary blackout on coverage of the explosion and urged media to refrain from publishing anything that may cause "fear in the public, panic and disorder and which may serve the aims of terrorist organisations".