DIYARBAKIR, Turkey, (Reuters) – Six members of the separatist Kurdistan Workers Party (PKK) were killed in a clash with Turkish military forces in southeastern Turkey late on Friday, security sources said.

The firefight broke out in a rural region of Siirt province after the guerrillas detonated an improvised explosive device under a minibus carrying schoolchildren, injuring two people.

Security forces said the clashes began after they launched an operation to find the group responsible for the attack.

More than 40 members of the separatist PKK and six soldiers have been killed this week.

Nearly 40,000 have been killed since 1984 when the PKK took up arms to carve out an ethnic homeland in primarily Kurdish southeast Turkey.

Turkey considers the PKK a terrorist organisation, as does the European Union and the United States.