Iran injected a new twist on Tuesday into the week-old American accusation of an Iranian plot to assassinate the Saudi ambassador to Washington, asserting that one of the defendants really belongs to an outlawed and exiled opposition group.

The defendant, Gholam Shakuri, identified by the Justice Department as an operative of the elite Quds Force of Iran’s Revolutionary Guards Corps, is actually a “key member” of the Mujahedeen Khalq, Iran’s Mehr News Agency reported.

The agency did not explain the group’s possible motive but left the implication that the plot was a bogus scheme meant to frame and ostracize Iran.

It said Mr. Shakuri, who is at large, had last been seen in Washington and in Camp Ashraf, the group’s enclave in Iraq. “The person in question has been traveling to different countries under the names of Ali Shakuri/Gholam Shakuri/Gholam-Hussein Shakuri by using fake passports including forged Iranian passports,” Mehr said.