Iran on Sunday denounced what it called Pakistan's inability to secure its own borders after five Iranian soldiers were kidnapped and taken into its eastern neighbour by Sunni extremists.
"We are unhappy with the Pakistani government over the abduction of our guards and their transfer to Pakistan," Fars news agency reported quoted police chief Esmail Ahmadi-Moghadam as saying.
Jaish-ul Adl, the rebel group formed in 2012 whose name in Arabic means Army of Justice, has said it was behind the kidnapping in Iran's restive southeast province of Sistan-Baluchestan.
The group posted pictures on its Facebook page it said were of the soldiers, handcuffed and being held in an unknown location.
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The foreign ministry in Tehran summoned Pakistan's charge d'affaires, demanding that Islamabad "act firmly against the leaders and members of the terrorist group who have fled into Pakistan", media reports said.
Home to a large Sunni minority and ethnic Baluch in a predominantly Shiite country, Sistan-Baluchestan province has been the scene of unrest in recent years.
Jaish-ul Adl said in November it assassinated a local prosecutor, and in October it ambushed Iranian border guards, killing 14.
In response, Iranian authorities executed 16 "rebels" -- eight Sunni insurgents and eight drug traffickers.
Another Sunni militant group Jundallah (Soldiers of God), whose leader Abdolmalek Rigi was hanged in June 2010, has also attacked civilians and officials in Sistan-Baluchestan.