Four of the rebels, members of the separatist Kurdistan Workers' Party (PKK), were killed after they crossed into Turkish territory in the mountainous province of Hakkari, which borders Iraq and Iran.

The sources did not say from which country they came.

Army chief Yasar Buyukanit Thursday argued publicly for a cross-border operation into neighbouring northern Iraq, where thousands of PKK militants have found refuge thanks to what Ankara charges is the tolerance of the local Iraqi Kurdish administration.

The fifth rebel was killed in the adjoining province of Sirnak.

Buyukanit said "large-scale" operations had been launched against the PKK in southeast Turkey with the advent of spring, the time when the rebels usually step up attacks as snow melts in the mountains, facilitating their movement.

Friday's clashes bring to at least 34 the PKK death toll since fighting intensified this month. The clashes have also claimed the lives of 10 soldiers.

The PKK, listed as a terrorist group by Ankara and much of the international community, took up arms for self-rule in the Kurdish-majority southeast in 1984. The conflict has resulted in more than 37,000 deaths.

Separately, a court in the western city of Izmir ordered Friday the arrest of five people, among them the deputy chairman of the local branch of Turkey's main legal Kurdish movement, the Democratic Society Party (DTP), who was identified only as Y.Y., Anatolia news agency reported.

The five are expected to stand trial on charges of praising an illegal organisation after they brandished portraits of jailed PKK leader Abdullah Ocalan and PKK flags at a Kurdish festival last month, the report said.