Iranian accusations of Western backing for Jundallah, the Sunni rebel group, may not be as fanciful as they seem.

Tehran often blames the United States and Britain for any internal unrest, including the uproar after President Ahmadinejad’s disputed re-election. But rumours of support for dissident militia groups such as Jundallah have far broader backing.

The group, which also calls itself the Iranian People’s Resistance Movement, was founded in 2002 and started its armed campaign in 2005. Its main cause is defending Shia Iran’s Sunni minority, concentrated in its poorest province, Sistan-Baluchistan.

As the Taleban evolved as Pakistan’s tool of influence in Afghanistan, so Jundallah evolved through shifting alliances with other parties.

Iran accuses the United States and Britain of backing Jundallah’s operations from Pakistani territory with Islamabad’s support, despite denials from the group. An outcry followed a 2007 ABC television report that alleged that US and Pakistani advice was given to Jundallah to help it in its attacks on Iran.

In 2008 the American journalist Seymour Hersh reported that United States congressional leaders had secretly agreed to President Bush’s $400 million (£245 million) funding request to give Washington a free hand in arming and funding militant groups such as Jundallah.

Meir Javedanfar, an Iranian Middle East analyst, told The Times that the success of yesterday’s attack could point to outside help. “It is possible that both are involved, since the British and Americans are involved in a tug-of-war in that region,” he said. “The fact remains that intelligence was of a better quality than in any other time. They managed to assassinate the deputy head of the Ground Forces. This is a huge hit for the Jundallah.”

The timing of the attacks, in the middle of delicate nuclear negotiations and on the eve of the next meeting, will convince Tehran that the West is closely involved. “It is a sign of weakness for Iran. The West has influence with this group and it is something they can use in talks with Iran,” he said.

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