Five Iranian border guards were killed Sunday during clashes with an armed group in the restive southeastern province of Sistan-Baluchistan, state media reported.
The guards were killed in Saravan, near Iran's border with Pakistan, the official IRNA news agency said.
Earlier, the judiciary's Mizan Online website had quoted local prosecutor Mehdi Shamsabadi as saying that six border guards were killed but later the number was revised down to five.
Sunday's attack was carried out by "a terrorist group that was seeking to infiltrate the country" but whose members "fled the scene after suffering injuries", IRNA said.
Iran foreign ministry spokesman Nasser Kanani condemned the attack saying Iran expects Pakistan to "crack down on terrorist groups" and "try to improve the security of the common borders".
"Certainly, the aim of these terrorist groups is to disrupt the security of the common borders and the security of the people living on the borders of the two countries," he added.
Pakistan strongly condemns terrorist attack
A spokesperson for Pakistan's Foreign Office issued a statement later on Sunday, stating that the country strongly condemns the terrorist attack in the Saravan region of Iran that resulted in the loss of lives of six Iranian security personnel.
"The government and people of Pakistan express their deepest condolences to the bereaved families of the martyrs as well as to the Iranian government over this tragic incident," Pakistan's Foreign Office said.
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"As reaffirmed during the recent meeting between Prime Minister of Pakistan and the President of Iran, we stress upon the need for mutual efforts to eliminate the terrorism on both sides of the border. Pakistan views Pak-Iran border as a border of peace and friendship; and remains committed to working with Iran towards the end," it added.
Poverty-stricken Sistan-Baluchistan, which also borders Afghanistan, is a flashpoint for clashes with drug smuggling gangs as well as with rebels from the Baluchi minority and with Sunni Muslim extremist groups.
The attack was one of the deadliest in the province in recent months.
On March 11, two policemen were shot dead during clashes with "criminals" in the same region, IRNA reported at the time.