"This is the first time they have used helicopters."

The website of the Patriotic Union of Kurdistan party, quoting witnesses, corroborated the report, adding that the aircraft flew at very low altitude over the villages.

The border guard official said the area was not considered a stronghold of the Party of Free Life of Kurdistan (PJAK), an Iranian Kurdish separatist group that appeared to have been the target of the raid.

There was no immediate comment from Iran.

The air raid, if confirmed, would be the first by the Iranian air force on the region.

Deadly clash

The incident comes a week after reports of a clash between Iranian police officers and suspected PJAK fighters in the country's western province of Kermanshah.

At least 10 policemen and 10 fighters were killed in the gun battle.

Kermanshah borders Iraq and is home to many of Iran's minority Kurds.

Iran's western provinces have been the scene of regular armed clashes between Iranian security forces and Kurdish separatists including PJAK, a group linked to Turkey's outlawed Kurdistan Workers' Party (PKK).

The PKK took up arms in 1984 to fight for a Kurdish homeland in southeast Turkey and is recognised by much of the international community as a terrorist group.

Some Iranian analysts said that PJAK fighters had bases in northeastern Iraq from where they operated against Turkey, Iran, and Syria.