"In an operation ... several members of the terrorist group PJAK (Party of Free Life of Kurdidstan) who were all Turkish were killed," Hojatollah Damyad, a security official at Kermanshah province governor's office, told Fars.

Damyad did not say whether the rebels were clandestinely based in Iran or had just crossed the border.

He also did not say when the operation took place, but added that four PJAK militants, including a 16-year-old girl, had been arrested in the city of Sanandaj in Kordestan province.

In recent years, Iranian forces have engaged in deadly clashes with the PJAK, which operates from rear-bases in northeastern Iraq.

The rebel group has close links with the Kurdistan Workers' Party (PKK), which has waged a deadly insurgency in southeastern Turkey since 1984.

Iran has also seen an upsurge in unrest in several regions with ethnic minority populations, including Baluchestan in the southeast, Arab-populated Khuzestan in the southwest and Kurdish-inhabited areas.