RIYADH, Saudi Arabia  Iranian officials claimed Monday that they had evidence of American and British involvement in the country’s worst suicide bombing attacks in years, raising tensions as Iran meets with Western nations for another round of delicate talks on its nuclear program.

At least five commanders of Iran’s elite Islamic Revolutionary Guards Corps were killed and dozens of other people were left dead and wounded on Sunday in two bombings in the restive southeast along Iran’s frontier with Pakistan, according to Iranian state news agencies.

The coordinated strike, one of the largest against the Guards in the region, appeared to mark an escalation in hostilities between Iran’s leadership and the Baluchi ethnic minority. Iranian officials accused foreign enemies of supporting the insurgents, singling out the intelligence agencies of United States, Britain and Pakistan.

Mohammad Ali Jafari, the Guards’ commander in chief, told the semiofficial ISNA agency on Monday: “Behind this scene are the American and British intelligence apparatus, and there will have to be retaliatory measures to punish them,” adding that Iran had documents proving their and Pakistani involvement.