By Mehreen Zahra-Malik
ISLAMABAD, March 26 (Reuters) - Pakistan has condemned the killing by Sunni Muslim militants of one of five Iranian border guards they have been holding hostage for the past six weeks, the foreign office said on Wednesday.
The guards were seized while patrolling the lawless frontier with Pakistan in early February. Jaish al-Adl (Army of Justice), an Iranian Sunni Muslim rebel group in Sistan-Baluchistan province later claimed responsibility.
The group said on its website on Sunday that it had killed the border guard.
"Pakistan is deeply saddened over the reported killing of one of the five Iranian border guards," the foreign office said in a statement.
"We condemn this terrorist act, and share the grief and agony of the families of the martyr and the other border guards."
Iran's semi-official Fars News Agency reported the killing on Monday and identified the victim as Jamshid Danaeefar.
Fars, quoting an "informed source", also said the four other hostages were in good health, without giving further details.
Some minority Sunni Muslims in Sistan-Baluchistan, an impoverished province bordering Pakistan, have rebelled against the Shi'ite government in Tehran. The lawless province is also used by drugs and arms traffickers.
The kidnapping has further inflamed tension between Tehran and Islamabad over sectarian violence. While Pakistan claims it has no evidence that the Iranian guards are in Pakistan, Iran accuses Pakistan of supporting the rebels.
Iranian Foreign Minister Javad Zarif expressed regret that "the government of Pakistan failed to provide security within its borders and prevent terrorists from using the country as a safe haven," according to official state news agency IRNA.
"Nuclear weapons do not bring external or internal security for any country - this is Iran's principle position," he said referring to Pakistan's possession of nuclear weapons.
Zarif added that he hoped that the kidnapped border guards would be returned soon,
"We hope the international community will not remain silent on this issue," he added.
Since the election of Prime Minister Nawaz Sharif, Pakistan has drawn much closer to Saudi Arabia, the center of Sunni power and Shiite Iran's main rival for influence in the Muslim world. (Editing by Susan Fenton)