Three American hikers who were arrested in Iran this summer after straying across its border with Iraq have been accused of spying, an Iranian state news agency reported on Monday.

The Tehran prosecutor told Iran’s official IRNA news agency that the Iranian authorities were pursuing espionage charges against the Americans, who were detained in late July after trekking through the Kurdistan region of Iraq and toward the Iranian border. News of the spying accusations drew a quick rebuke from the White House and Secretary of State Hillary Rodham Clinton, with each reiterating calls for the Iranians to release the hikers, Shane M. Bauer, 27, of Emeryville, Calif.; Joshua F. Fattal, 27, of Cottage Grove, Ore.; and Sarah E. Shourd, 31, of Oakland, Calif.

“We believe strongly that there is no evidence to support any charge whatsoever,” Mrs. Clinton told reporters in Berlin. “And we would renew our request on behalf of these three young people and their families that the Iranian government exercise compassion and release them so they can return home.”

The White House press secretary, Robert Gibbs, said the three were innocent.

It was unclear whether Iran had formally filed legal action against the hikers, or whether prosecutors were merely leveling accusations for public consumption. The Persian word used by the chief prosecutor who discussed the case can mean either “charged” or “accused” in English.