The soldiers were on a security sweep of rural ground near the town of Semdinli in Hakkari province when rebels from the Kurdistan Workers' Party (PKK) hurled a hand grenade at the unit, the source said.

An operation was under way to catch the attackers.

The PKK, listed as a terrorist group by Ankara and much of the international community, has been fighting for self-rule in Turkey's mainly Kurdish southeast and east since 1984, in a conflict that has claimed some 45,000 lives.

Last month, the rebels had announced that they were extending a ceasefire in their campaign until September 1 in anticipation of a peace plan to be announced by their jailed leader Abdullah Ocalan.

They warned, however, that they would defend themselves if they came under attack from the Turkish military.

Ankara, which has never recognised the PKK's unilateral truces, is working on its own package of reforms to boost the rights of its Kurdish community and encourage the PKK rebels to lay down arms.