By Seyhmus Cakan
DIYARBAKIR, Turkey (Reuters) - Kurdish militants killed two police officers in a car bomb attack on a checkpoint in southeast Turkey on Sunday, as authorities imposed a curfew in the region's largest city Diyarbakir where clashes broke out, security sources said.
Turkish forces backed up by helicopters and commandos shelled a mountainous area where the Kurdistan Workers Party (PKK) fighters had fled after the checkpoint attack in Sirnak province, killing six of them, the sources added.
A police officer was reported killed in another confrontation.
Hundreds of militants and more than 100 police and soldiers have died since a ceasefire collapsed in July, shattering a peace process launched in 2012. It is the worst violence Turkey has seen in two decades.
The Diyarbakir governor's office said it had placed the central historic Sur district under a round-the-clock curfew. Security sources said seven police officers were wounded in clashes there.
In other central areas of the city, police fired tear gas and water cannon at small groups of youths who threw stones and tried to set up street barricades in protest against the curfew.
Speaking to reporters near the Sur district, the leader of the pro-Kurdish Peoples' Democratic Party (HDP), Selahattin Demirtas, called for the Turkish state and PKK leadership across the border in Iraq's Qandil mountains to halt the violence and return to peace talks.
"Both Ankara and Qandil must take a position that responds to the people's expectation with a clear, concrete project," he said. "Even if the peace (talks) table has been upturned it is in our power to put it up again."
ROCKETS, SHELLS, FUNERALS
The PKK began its separatist insurgency in 1984, triggering a conflict that has killed more than 40,000 people. The group, which says it is now fighting for greater Kurdish autonomy, is designated a terrorist organization by Turkey, the European Union and the United States.
President Tayyip Erdogan has promised the fight will go on until "not one terrorist is left". The conflict has flared up as Turkey prepares for a snap parliamentary election on Nov. 1 after a June vote was inconclusive.
The PKK also launched an attack on Sunday with rocket-propelled grenades and rifles in the Silvan district of Diyarbakir province, killing one police officer and wounding another, one security source told Reuters. Locals officials said they also declared a curfew in that area.
The Sirnak governor's office said it declared a new curfew from 7 p.m. (1600 GMT) in Cizre, near the Syrian and Iraqi borders, just 36 hours after the expiry of a previous eight-day round-the-clock curfew in the town.
Thousands of people gathered in the town on Sunday for the funerals of 16 people killed during the week and who were buried alongside each other, witnesses said.
The HDP has said 21 civilians were killed during clashes in the town while under curfew. The government said one civilian and 32 militants died.
State-run Anadolu Agency reported Culture and Tourism Minister Yalcin Topcu as saying the recent security forces' operations had hit the PKK hard.
"A significant portion of the mountain forces has been destroyed. Their structures in the cities are being ripped out and cast aside," he said.
(Reporting by Seyhmus Cakan; Writing by Daren Butler; Editing by Raissa Kasolowsky and Andrew Heavens)