An Iranian guard was killed in a fight with an armed group near the western border with Iraq, local media reported on Monday.
Iran's armed forces have been stepping up their presence along its borders to prevent smuggling, illegal immigration and militant infiltration.
"Last night around 9 p.m., the border guards who were trying to stop armed smugglers entering the country had a fight with armed bandits," Tasnim news agency quoted Kiumars Sheikhi, commander of the border guards in Kermanshah province as saying.
He said a member of the Baneh county border patrol had been killed in the fight.
Sheikhi said members of the armed group were planning a sabotage operation in Iran, but did not give details or say whether they were connected to militant groups.
In July, militants killed 10 Iranian Revolutionary Guards in an attack on a post on the Iraqi border, an area where armed opposition Kurdish groups are active.
Islamic State militants have also entered Iran via the border with Iraq, which is left porous by poor coordination between Iranian and Iraqi security forces.
Attacks against police officers and border guards are also common along Iran's border with Pakistan. A suicide bomber from a Sunni militant group killed 27 members of the elite Revolutionary Guards last month in a southeastern region which has seen a rise in attacks by Sunni militants based in Pakistan.
Border guards trying to defend against militant groups in the impoverished provinces have faced criticism for shooting at smugglers.