"Vali Haji-Gholizadeh was shot dead at his door step" in the town of Khoy, on the border with Turkey, Fars news agency said.

The agency said the attackers fled the scene and apparently left behind no traces, but added the slain prosecutor had been "threatened in the past few days."

"He had a brilliant record in battling counter-revolutionaries, land-grabbing and moral corruption," Fars reported.

Northwestern Iran, which has a sizeable Kurdish population, has seen deadly fighting in recent years between Iranian security forces and members of the Party of Free Life of Kurdistan (PJAK) as well as other Kurdish rebels operating from bases in neighbouring Iraq.

The group is closely allied with the Turkish Kurdish rebel group, the Kurdistan Workers' Party (PKK), which is listed as a terrorist group by Ankara and much of the international community.

Iraq, Iran, Syria and Turkey all have significant ethnic Kurdish minorities.