The Iranian security men were killed in a clash with Sunni militants who had infiltrated from Pakistan's Balochistan province.
Foreign Office spokesperson Tasnim Aslam said that in case the culprits have crossed over to Pakistan after committing the crime on Iran's soil, they will be apprehended and brought to justice.
She added that Pakistan strongly condemns this act of terrorism and conveys sincere condolences to the bereaved families and the government of Iran.
Jais al Adl militant group has claimed responsibility for the attack.
It said that its fighters ambushed two patrols of the Iranian border guards in Negwar border area.
"As a result of this attack, eight members of Iranian border guards killed and several weapons are seized from the enemy. All the fighters of Jaish Aladl are managed to return safely," it said in a statement.
The groups said that a video of this attack was recorded and soon will be released.
The incident occurred ahead of Iranian Foreign Minister Javad Zarif's two-day visit to Pakistan who is expected on Wednesday to discuss the crisis in Yemen.
After the attack, it is believed that Zarif will also discuss the state of bilateral ties, including attack by militants across the border in the Iranian province of Sistan-Balochistan.
The clash was the deadliest since October 2013 when 14 border guards were killed in an attack claimed by Sunni militant group Jaish-ul Adl (Army of Justice).

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