Iran's elite Revolutionary Guard promised a "crushing" response to an attack that killed several senior commanders, state television said on Monday, as the death toll from the deadliest such incident in years rose to 42.
In neighboring Pakistan, a Foreign Ministry spokesman condemned Sunday's suicide bombing in southeastern Iran near the Pakistani border and denied suggestions from Iran that security agents in Pakistan were cooperating with the perpetrators.
The attack in Sistan-Baluchistan province, which killed the deputy head of the Guard's ground forces, highlighted deepening instability in a region of mainly Shiite Muslim Iran bordering Pakistan and Afghanistan.
Many minority Sunnis live in the impoverished area, which has seen an upsurge in bombings and other violence.
English-language Press TV said civilians and tribal leaders were among the victims, in what was one of the deadliest such attacks in the Islamic Republic in recent years.
On Sunday, state media said a local rebel Sunni group called Jundallah — or God's soldiers— claimed responsibility for the attack.
In May, Jundallah said it sent a suicide bomber into a Shiite mosque in the southeastern city of Zahedan, killing 25 worshippers.
The latest attack, however, would mark the group's highest-level target.
It also raised questions about how the attacker breached security around such a top delegation from the Revolutionary Guard — the country's strongest military force, which is directly linked to the ruling clerics under Supreme Leader Ayatollah Ali Khamenei.
Jundallah accuses Iran's Shiite-led government of discrimination against Sunnis in the remote desert region, has been blamed for many deadly incidents over the last few years.
Iranian officials also accused the United States and Britain of involvement, a charge rejected by Washington.
The bombing and allegations of foreign involvement risk overshadowing talks between Iranian and Western officials in Vienna later on Monday intended to help resolve a standoff with the West about Iran's nuclear ambitions.
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