At least 10 Iranian border guards have been killed in an overnight attack by unidentified gunmen near the border with Iraq, according to media in Iran.

The incident took place near the town of Marivan, in a Kurdish area of Iran some 620km west of the capital, Tehran, according to the semi-official Fars news agency.

“The attack by the evil rebels and terrorists against a revolutionary border post and the explosion of a munitions depot caused the martyrdom of 10 fighters,” a statement by the Islamic Revolutionary Guard Corps, as quoted by the semi-official Tasnim news agency, said on Saturday.

Provincial security official Hosein Khosheqbal told state television that 11 members of the Guards’ voluntary Basij forces were killed in the overnight violence in Marivan, which he blamed on the Kurdish armed opposition group The Party of Free Life of Kurdistan (PJAK).

“The latest news is that the Basij [the government-aligned militia] and Guards forces are in hot pursuit of the attackers,” Khosheqbal said.

It was not immediately clear why there was a discrepancy in the number of fatalities reported.

It was the largest number of Iranian troops killed in a single attack on the border with Iraq in recent years, though the area has seen occasional fighting between Iranian forces and Kurdish separatists as well as fighters linked to the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group.

Earlier this month, the Guards said they had killed three fighters in a security operation near the border with Iraq. Nine others were reported killed by the Guards last month further north on the border.

There is little coordination between Iranian and Iraqi forces over security of the porous border that has also been used by ISIL to enter Iran.

Intelligence Minister Mahmoud Alavi said on Tuesday that security forces in southwest Iran arrested four suspected ISIL operatives who were planning attacks.

In June 2017, ISIL fighters carried out coordinated attacks at the parliament building in Tehran and the mausoleum of Iranian revolutionary leader Ayatollah Ruhollah Khomeini south of the capital, killing at least 18 people.