An American freelance journalist detained in Iran for three months has been charged with spying.

Roxana Saberi, who was filing stories for National Public Radio (NPR) in the United States, was arrested in January in Tehran after buying a bottle of wine.

Ms Saberi, a dual Iranian-American national, had her press credentials revoked in 2006 after three years in Iran but continued to live there researching a book and a master’s degree.

Tehran's deputy prosecutor, Hassan Haddad, said that her case had been forwarded to the revolutionary court and that she had accepted all the charges against her.

NPR confirmed that Ms Saberi had continued to file short reports but that the Iranian Government had “tolerated” her doing so. Several other Iranian-Americans have been arrested in recent years, however, apparently prompted by fears that they were fomenting dissent against the Government.

Ms Saberi "was carrying out spying activities under the guise of being a reporter", Mr Haddad was quoted as saying by Iranian media on Wednesday.

"The evidence is mentioned in her case papers and she has accepted all the charges,” he said, adding that he would provide more details "after the verdict is given".

Ms Saberi's lawyer, Abdolsamad Khorramshai, said that he had yet to see the charges against his client, so did not know how serious they were. "There are different punishments for different levels of spying," he said.

Iran disclosed Ms Saberi’s detention in February after her worried parents in Fargo, North Dakota, spoke out about her disappearance. She had called them to say that she had been arrested after buying a bottle of wine and expected to be released soon.

On Monday, her parents were allowed to visit her in Tehran’s notorious Evin prison, where she was sharing a cell with three others. They said she seemed to be in relatively good health.

Iran does not recognise dual citizenship and legally she is regarded as Iranian. "Saberi has an Iranian citizenship, passport and an Iranian national identity card," Mr Haddad said. "She has entered Iran as an Iranian citizen and if she has another citizenship, we are unaware of it and it has no effect on how we will proceed with her case."

Hillary Clinton, the US Secretary of State, said last week that the US had given a letter to Iranian officials during a meeting in the Netherlands, seeking Iran's help in resolving Ms Saberi's case and those of Robert Levinson and Esha Momeni, two other Americans missing or detained in Iran.

The US has had no diplomatic relations with Tehran since the siege of its embassy there in 1979 and tensions remain high over Iran's apparent ambitions to build a nuclear weapon, despite President Obama’s pledges to forge a new relationship.

Ms Momeni, another dual national, who was arrested in October for supporting a campaign for women’s rights, is free but not allowed to leave the country.

Mr Levinson, a private detective investigating cigarette smuggling, disappeared in 2007 on the Iranian island of Kish, but Tehran has repeatedly denied that he is in the country.

Iran is seeking the release of three Iranian diplomats held without trial by US forces in Iraq since 2007.

Tensions are expected to rise again tomorrow, Iran’s National Nuclear Day, when President Ahmedinejad is expected to boast of Tehran’s latest nuclear progress.

David Miliband, the British Foreign Secretary, on a visit to Saudi Arabia, called for a “united front” between Gulf Arab countries and global powers to deal with Iran’s nuclear ambitions.

“I know that many countries in the region are concerned,” Mr Miliband told reporters. “I think it’s very important that there is a united front between the countries of Europe, America, Russia and China and countries of the Gulf in addressing the range of issues that are posed by the Iranian regime.”

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