The landmine, believed to have been planted by Kurdistan Workers' Party (PKK) rebels, exploded when a bus carrying soldiers and village guards -- local Kurdish men supporting the army against the militants -- was passing the town of Semdinli.

The explosion also wounded three other village guards, the source said.

The PKK frequently uses landmines to attack security forces.

The Turkish army often uses civilian vehicles to transfer troops in the region in a bid to thwart possible attacks by the separatist group.

The PKK, listed as a terrorist organisation by Ankara and much of the international community, has been fighting for Kurdish self-rule in Turkey's mainly Kurdish east and southeast since 1984. The conflict has claimed more than 37,000 lives.