TEHRAN: Iran has charged three detained US citizens with espionage, the official IRNA news agency quoted a prosecutor as saying on Monday, but Secretary of State Hillary Clinton said there was no evidence to back the charges.

The three, Shane Bauer, 27, Sarah Shourd, 31, and Josh Fattal, 27, were held after they crossed into Iran from northern Iraq at the end of July. Their families said they strayed across the border accidentally.

“The three are charged with espionage,” Tehran general prosecutor Abbas Jafari Dolatabadi told IRNA. “Investigations continue into the three detained Americans in Iran.”

The United States has sent strong messages to Iran urging the release of the three hikers, calling on the authorities to exercises “compassion” toward the three Americans.

“We believe strongly that there is no evidence to support any charge whatsoever,” Clinton said in Berlin on Monday. “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, and we will continue to make that case,” she added.

Iranian President Mahmoud Ahmadinejad suggested in an interview with the American television network NBC in September that the Americans’ release might be linked to the release of Iranian diplomats he said were being held by US troops in Iraq. Under Iran’s law, espionage is a crime that is punishable by death.