The head of Iran's Revolutionary Guard threatend to retaliate against the United States and Britain following a suicide bombing that killed 42 people, including 6 commanders of the Guards.

Media reports out of Iran say a Sunni Muslim group called Jundollah claimed responsibility for Sunday's attack in Sistan-Baluchestan province. But Guards commander-in-chief Mohammad Ali Jafari said Iranian security officials have documents indicating "direct ties" from Jundollah to U.S., British and, "unfortunately," Pakistani intelligence organizations, the ISNA news agency said.

"Behind this scene are the American and British intelligence apparatus, and there will have to be retaliatory measures to punish them," Jafari said.

The U.S., Britain and Pakistan have all condemned the bombing, and denied any involvement.

"We reject in the strongest terms any assertion that this attack has anything to do with Britain," said a spokeswoman at Britain's Foreign Office. "Terrorism is abhorrent wherever it occurs."

But Iran doesn't believe it. General Mohammad Pakpour, commander of the Guards' ground forces, said on Iranian television, "The base of the terrorists and rebels has not been in Iran. They are trained by America and Britain in some of the neighboring countries."

Jundollah says it is fighting to end discrimination against Sunni Muslims by Iran's dominant Shi'ites. Jundollah operates out of a Sunni area in Iran along the border with Pakistan and Afghanistan. Its leader is Abdolmalek Rigi.

"This person himself and his plans are undoubtedly under the umbrella and the protection of these (U.S., British and Pakistani) organizations," Jafari said.

The incident is threatening to raise tensions at meetings in Vienna Monday to discuss Iran's nuclear program. Analysts also fear the bombing will be used an an excuse to further clamp down on moderates opponents of Iranian President Mahmoud Ahmadinejad.