A suicide truck bombing at a police headquarters in Turkey's largely Kurdish southeast killed at least 11 and wounded dozens on Friday, two days after Turkey launched an incursion against Islamic State and Kurdish militia fighters in Syria.
Prime Minister Binali Yildirim said there was no doubt that the Kurdistan Workers Party (PKK), which has waged a three-decade insurgency for Kurdish autonomy, was responsible for the attack in Sirnak province, which borders Syria and Iraq.
The provincial governor's office said 11 police officers were killed and 78 people, three of them civilians, wounded. There was no immediate claim of responsibility.
The bombing in the town of Cizre was the latest in a series of attacks since a ceasefire with the PKK collapsed more than a year ago, and comes as Turkey tries to recover from a failed July 15 military coup.
More than 1,700 military personnel have been removed for their alleged role in the putsch, including some 40 percent of admirals and generals, raising concern about the NATO member's ability to protect itself as it battles Islamic State in Syria and Kurdish militants at home.
At a news conference in Istanbul, Yildirim said Turkey had opened a war on all terrorist groups. His deputy, Numan Kurtulmus, said on Twitter that Islamic State, the PKK and the Syrian Kurdish YPG militia were all attacking Turkey to take advantage of last month's coup attempt.
"Turkey is in an intense fight against terrorist organizations ... The PKK/YPG and Islamic State seized the July 15 coup attempt as an opportunity," Kurtulmus wrote.
Large plumes of smoke billowed from the blast site in Cizre, footage on CNN Turk showed. The broadcaster said a dozen ambulances and two helicopters had been sent to the scene.
Photographs broadcast by private channel NTV showed a large three-storey building reduced to its concrete shell, with no walls or windows, and surrounded by grey rubble.
Turkish special forces, tanks and warplanes launched their first major incursion into Syria on Wednesday in support of Syrian rebels, in an operation President Tayyip Erdogan has said is aimed both at driving Islamic State away from the border area and preventing territorial gains by the YPG.
Turkey views the YPG as an extension of the PKK, which is listed as a terrorist organization by Turkey, the United States and the European Union. More than 40,000 people, mostly Kurds, have died since the rebels took up arms in Turkey in 1984.
Turkish troops fired on U.S.-backed YPG fighters in northern Syria on Thursday - a confrontation that highlights the cross-cutting of interests of two pivotal NATO allies.
Also on Thursday, Interior Minister Efkan Ala accused the PKK of attacking a convoy carrying the country's main opposition party leader, Kemal Kilicdaroglu.
The government has blamed the PKK for a series of attacks this month in the southeast. The group has claimed responsibility for at least one attack on a police station.
Last week Erdogan accused followers of a U.S.-based Islamic cleric he blames for the July 15 coup attempt of being complicit in attacks by Kurdish militants.
The cleric, Fethullah Gulen, has denied any involvement in and denounced the coup plot.