Islamabad has lodged a formal protest with Tehran about an attack by militants who killed six Pakistani paramilitary troops as they were patrolling a mountainous area near the Iranian border.
Pakistan's Foreign Ministry says it summoned Iran's ambassador to demand that Tehran take action against the armed group responsible for the attack in Pakistan's southwestern province of Balochistan.
Pakistani authorities say about 30 militants attacked a convoy of forces from Pakistan's Frontier Corps on December 14, killing six soldiers and wounding 14.
Islamabad says four attackers were killed in the clash.
There was no immediate claim of responsible for the ambush along a mountainous stretch of road in Balochistan Province's Kech district.
Neither Pakistan nor Iran has identified who they believe was responsible and there was no immediate claim of responsibility for the attack.
Islamist militants linked to the Taliban, Al-Qaeda, and Islamic State have been operating in the province, which also borders Afghanistan.
Ethnic Baluch militants are also waging an insurgency against the central government in Balochistan.
Iran on December 15 condemned the attack and vowed to cooperate with Islamabad.