DIYARBAKIR, Turkey (Reuters) - Ten Turkish soldiers and eight civilians were killed on Sunday when suspected Kurdish militants detonated a five-tonne truck bomb that ripped through a checkpoint near a military outpost in the country's southeast, the prime minister said.
Another 27 people, including 11 soldiers, were wounded in the blast which hit the Durak gendarmerie station, 20 km (12 miles) from the town of Semdinli, in one of the most deadly attacks in the region of recent times.
The mountainous Hakkari province, where the attack occurred, lies near the border with Iraq and Iran and is one of the main flashpoint areas in a conflict that has pitted Turkey's army against the militant Kurdistan Workers Party (PKK) for 32 years.
The attack occurred around 9:45 am (0645 GMT) when a small truck approached the vehicle checkpoint and ignored an order to stop, prompting gendarmerie troops to open fire, the Hakkari governor's office said.
A bomb in the vehicle was detonated, which Prime Minister Binali Yildirim told reporters contained some five tonnes of explosives.
President Tayyip Erdogan vowed to put an end to PKK attacks as he condemned the bombing, accusing the group of acting on behalf of "dark forces that had designs in Syria and Iraq".
"Hand in hand with our people, our state with all its institutions is determined to make the separatist terror organisation incapable of carrying out attacks," his written statement said.
The army has "neutralised" 387 PKK fighters in Hakkari alone since Aug. 4, state-run Anadolu Agency cited military sources as saying.
The governor's office said extensive air-backed operations were being conducted by commando units in the area to capture PKK militants, who were believed to have opened fire in the run-up to the attack to distract soldiers at the checkpoint.
Military helicopters flew the wounded to hospitals in the region following the blast, the governor's office said, as soldiers looked on and locals wandered amid mangled wreckage and debris, video footage on CNN Turk showed.
Authorities were on high alert for possible attacks on Sunday, 18 years to the day since PKK leader Abdullah Ocalan fled Syria before being captured by Turkish special forces in February the following year.
He has since been in prison on an island near Istanbul.
Erdogan often criticises what he sees as inadequate Western support in the fight against the PKK, and Energy Minister Berat Albayrak called on Sunday on its allies to show solidarity.
"This fire of terror continues to burn our country, the whole region and world each day that passes. We have to show more sincerity than ever in this process," Albayrak said in a speech at an energy conference in Istanbul.
Violence has flared in the mainly Kurdish southeast and elsewhere in Turkey in recent days.
On Saturday, a man and a woman who authorities suspect were PKK militants preparing a car bomb attack detonated explosives and killed themselves near the capital Ankara in a stand-off with police.
In the southeast, 12 people were killed on Saturday, including eight PKK fighters. Four civilians were killed by gunfire from an armoured police vehicle in the town of Yuksekova near the Iranian border.
On Thursday, a bomb attack near a police station in Istanbul wounded 10 people. The Kurdistan Freedom Hawks (TAK), a PKK offshoot, claimed responsibility for that blast.
The PKK, which launched its separatist insurgency in 1984, is designated a terrorist organisation by Turkey, the United States and the European Union.
A two-year ceasefire between the group and Turkish authorities collapsed in July last year and the violence subsequently rose to levels not seen since the height of the conflict in the 1990s.
The surge in violence coincides with a Turkish military operation in northern Syria in support of rebels and designed to drive away from the border Islamic State militants and a Syrian Kurdish militia closely linked to the PKK.
President Erdogan chaired a security summit with the head of the armed forces and ministers in Istanbul on Saturday, but details of the meeting have not been disclosed.
Writing by Daren Butler; editing by John Stonestreet