Bomb blasts in two cities in southeast Turkey killed nine civilians and wounded dozens on Wednesday, security sources said, blaming the Kurdistan Workers Party (PKK) for the coordinated attacks targeting police.
A PKK commander warned at the weekend of fresh attacks, saying police "will not be able to live as comfortably as they did in the past in cities."
Earlier in the day, four soldiers were killed and nine wounded when militants opened fire with rockets and long-range weapons from across the Iraqi border. Security sources also blamed that attack, in Sirnak province, on the PKK.
Turkey's mainly Kurdish southeast has seen its worst violence in two decades since the PKK abandoned a 2-1/2-year ceasefire last year.
Four civilians were killed when roadside explosives were detonated by remote control near a hospital in the town of Kiziltepe in Mardin province, near the Syrian border, in an attack targeting a bus carrying police, the sources said.
About 30 civilians and 10 police officers were wounded.
In the region's largest city, Diyarbakir, five civilians were killed in a car bomb attack apparently targeting police, the sources said. They said 12 people were wounded in that attack, including five police officers.
A PKK commander, Cemil Bayik, said "a new style of war has been developed" in an interview published on Sunday by the Firat news agency, which is close to the group.
"The war will from now on be conducted everywhere without distinguishing between mountains, valleys and cities," he said.
Turkey is dealing with the aftermath of a failed coup attempt on July 15 which killed more than 240 people and wounded 2,200.
More than 60,000 people, including many in the military and police have been detained, suspended or placed under investigation since the coup attempt, in which rogue soldiers commandeered tanks and warplanes to try to take power.
The PKK, designated a terrorist organisation by Turkey, the European Union and the United States, took up arms against the Turkish state in 1984 and more than 40,000 people, mainly Kurds, have died in the violence.