The verdict -- the harshest sentence ever meted out to a dual national on security charges in Iran -- was greeted with shock by her father, who said Saberi had been "tricked" into confessing.

Saberi, 31, has been detained in the notorious Evin prison in Tehran since January and went on trial behind closed doors on Monday accused of spying for the United States.

"Ms Saberi has been sentenced to eight years in jail and I am going to appeal," her lawyer Abdolsamad Khoramshahi told AFP. Under Iranian law, the verdict can be appealed within 20 days.

The case against Saberi, who has both US and Iranian nationality, has raised deep concerns in Washington and among rights groups.

She was initially reported to have been detained for buying alcohol, an illegal act in the Islamic republic.

The ISNA news agency, quoting an unnamed judiciary source, confirmed that a revolutionary court had sentenced Saberi for espionage -- a charge that could have risked the death sentence. No date was given for the verdict.

"Roxana said in court that her earlier confessions were not true and she told me she had been tricked into believing that she would be released if she cooperated," her father Reza Saberi told AFP.

"Her denial is documented in her case but apparently they did not pay attention to it," he added, without saying when he had spoken to his daughter.

"We are very shocked and we were not expecting it. We were hoping for six months and then clemency."

The court ruling comes despite calls by US Secretary of State Hillary Clinton for Saberi's release and President Barack Obama's diplomatic overtures to Iran after three decades of ruptured ties.

Several US-Iranians, including academics, have been detained in recent years on security charges, but released after several months behind bars.

US-born Saberi, who is also of Japanese descent, has reported for US-based National Public Radio (NPR), the BBC and Fox News, and had lived in Iran for six years.

The BBC said in a statement issued in London it was "extremely concerned at this severe sentence".

"Roxana was tried in secret and no evidence of espionage has been made public," it said.

Iran's foreign ministry spokesman Hassan Ghashghavi said in March that Saberi's press card had been revoked in 2006 and since then she had been working "illegally".

Earlier this month Tehran's deputy prosecutor Hassan Haddad said Saberi was carrying out "spying activities under the guise of being a reporter."

Haddad said Saberi had entered Iran, which does not recognise dual nationality, as an Iranian citizen and "there is no evidence that she has another citizenship."

Last month, Saberi's parents -- who came to Iran to pursue her case and have visited her at least twice -- appealed to Iranian supreme leader Ayatollah Ali Khamenei for her release, saying she was in a "dangerous" mental state.

US State Department spokesman Robert Wood on Wednesday branded the trial "less than transparent" and said the charges against her were "baseless".

A website freeroxana.net has been set up by her friends and university alumni, and the Committee to Protect Journalists also launched a petition calling for her release.

The website said Saberi was chosen Miss North Dakota in 1997 and was among the top 10 finalists for Miss America the following year.

Clinton said she had delivered a letter to Iranian officials on March 31, seeking Saberi's release and making appeals on behalf of two other US citizens.

Robert Levinson, a former FBI agent, vanished on the Gulf island of Kish two years ago, and student Esha Momeni has been prevented from leaving Iran despite being released from jail last year.

After three decades of severed ties, the Obama administration has called for dialogue with Tehran over its controversial nuclear drive, which Western powers fear could be a cover for efforts to build an atomic bomb.

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