Six Turkish soldiers were killed on Friday in a clash with Kurdish militants in the southeast of the country while two more lost their lives when a military helicopter sent to the scene crashed, the army said.

The six troops were killed and eight others wounded in fighting with members of the outlawed Kurdistan Workers' Party (PKK) near a military base in the Cukurca district of Hakkari province.

A Cobra helicopter despatched to the scene then crashed due to a technical problem, resulting in the deaths of the two pilots, the army added.

Turkish F-16 jets, helicopters and drones were scrambled to fight the "terrorists" behind the attack and reinforcements were sent to the area.

So far, six PKK militants have been "neutralised" in the follow-up operations which are continuing, the army said.

Pro-PKK news site Firat news claimed that the helicopter had been downed by PKK fighters.

In a separate operation in the neighbouring Sirnak province, 15 PKK members have been killed, the army said.

Turkey has been waging an offensive against the PKK after the collapse in 2015 of a two-year ceasefire declared by the group.

Hundreds of members of the Turkish security forces have been killed in attacks since then, with funerals of army personnel being laid to rest in front of grieving relatives a daily event on national television.

But President Recep Tayyip Erdogan vowed that despite the latest attack the fight against the PKK "will continue with determination".

"No clash, no ambush, will prevent us from defending Turkey's unity," he said in a statement.

"As long as the nation stands behind our brave security forces, Turkey will rid itself of these bloody organisations and dirty alliances," he added.

- 'Nothing of our house left' -

On Thursday night, four PKK militants said to have been loading explosives onto a stolen truck were killed in a huge explosion in an area near Diyarbakir in the southeast that was felt throughout city.

The explosives detonated prematurely, the interior ministry said.

Dozens of local residents gathered on Friday to inspect the huge crater left by the immense blast, whose power also blew out walls and windows of nearby homes, an AFP correspondent said.

"I was lying in my bed. Suddenly an explosion went off, the glass in the windows exploded and I was covered in glass," said local resident Mehmet Emin Akyuz.

"There were body parts everywhere. There's nothing left of our house," he told AFP.

That incident came hours after at least eight people including soldiers were injured by a remotely-detonated car bomb aimed at a military vehicle in Istanbul.

There was no immediate claim of responsibility for the car bomb. But the official Anatolia news agency said eight people had been detained, including PKK members.

On Tuesday, three people were killed and 42 others wounded when a car bomb attack claimed by the PKK struck a police vehicle in Diyarbakir.

The PKK is listed as a terrorist group by Ankara and its Western allies but Erdogan has repeatedly accused the European Union and United States of not doing enough to halt its activities.

Over 40,000 people have been killed since the PKK took up arms in 1984 demanding a homeland for Turkey's biggest minority. Since then, the group has pared back its demands to focus on cultural rights and a measure of autonomy.