Iran says all three countries have links to a Sunni group blamed for Sunday's suicide blast that killed at least five senior members of Iran's Revolutionary Guard.
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Iran stepped up accusations on Monday against the US, Britain, and Pakistan, saying all three countries have links to a Sunni group blamed for Sunday's suicide blast that killed more than 40, including at least five senior members of Iran's Revolutionary Guard.
Tehran said it would demand that Pakistan hand over the attack's suspected mastermind. It said the country's intelligence agency, along with those of the US and Britain had a hand in planning and directing the attack.
The accusations are likely to ratchet up tensions between Iran and the West, which are already high over Iran's nuclear program.
The US, Britain, and Pakistan have all denied any involvement in Sunday's attack.
A Sunni rebel group, Jundallah, claimed responsibility for the attack in Pasheen, in southeast Iran near the border with Pakistan. The group has long waged an anti-government insurgency in the Sistan and Baluchistan region, claiming Tehran discriminates against the area's Baloch ethnic minority. (See map here.)