According to the governor's office in Sirnak province on Thursday, the military has intensified anti-rebel operations lately following intelligence reports that hundreds of rebels have infiltrated into Turkey from neighbouring Iraq.
Three Turkish soldiers and a government-paid village guard were also killed during the clash in an area, some 40km away from the Iraqi border, the governor's office said in a statement.
The anti-rebel operation was launched on Tuesday and the clash occurred in an area between the town of Pervari, in Siirt province and the town of Eruh in Sirnak province.
A military official said Turkish commandos were reinforced from the air by US-made Cobra attack helicopters against the guerrillas.
Among the Turkish troops killed were a lieutenant and two sergeants, along with the village guard, armed and paid by the government, the statement said.
Violence has increased since June, when the rebels declared an end to a five-year old unilateral truce, saying that Turkey had not reciprocated.
The rebels declared the cease-fire in 1999, following the capture of their leader Abdullah Ocalan. Earlier this month, Turkish troops killed nine rebels in a five-day clash on the Iraqi border.
The rebels belong to the Kurdistan Workers' Party, or PKK, which has been seeking autonomy in Turkey's southeast and has battled government forces since 1984 - a conflict that has killed more than 37,000 people.
Speaking to Aljazeera.net on Thursday, Turkish analyst Professor Husain Bogci said he feared the conflict would only get worse.
"Naturally, the EU may jump on this to throw yet another obstacle into the accession talks. But when we look at the funding for this rebel group – we see they have many assets in Europe.
"The question comes down to what Europe wants to define as terrorism and whether any country can allow armed groups to cross internationally recognised borders in order to affect some kind of ill-defined and violent change.
"However, I am certain that while debate goes on at the political level – the Turkish military is bound to respond to the growing numbers of Kurdish rebels coming into the country. But Ankara is getting major cooperation from Iran, Iraq and Syria in this regard."