An American journalist convicted in Iran of spying for the United States (US) has gone on a hunger strike to protest her imprisonment, her father said yesterday.

Roxana Saberi, a dual American-Iranian citizen who will turn 32 today, was sentenced to eight years in prison after a swift, one-day trial behind closed doors less than two weeks ago. Yesterday was the fifth day of her hunger strike, her father told The Associated Press.

"She went on a hunger strike Tuesday to protest her imprisonment," her Iranian-born father, Reza Saberi, said. "She will remain on hunger strike until she is freed."

The case has been a source of tension between the US and Iran at a time when the Obama administration has said it wants to engage its longtime adversary. The US has called the accusations against Saberi baseless and demanded her release.

Saberi's father said her lawyer appealed the court's ruling yesterday - less than a week after Iran's judiciary spokesman said an Iranian appeals court would reconsider her verdict, an indication her sentence could be commuted.

Serious allegation

Iran's judiciary chief has ordered a full investigation into the case, and President Mahmoud Ahmadinejad has urged Tehran's chief prosecutor to ensure Saberi be allowed a full defence during her appeal.

Saberi was arrested in late January and initially accused of working without press credentials. But earlier this month, an Iranian judge levelled the far more serious allegation of espionage.

Saberi, who was born in the US and grew up in Fargo, North Dakota, moved to Iran six years ago and worked as a freelance journalist for news organisations, including National Public Radio and the British Broadcasting Corp. She received Iranian citizenship because her father was born in Iran.

Iran has released few details about the charges against Saberi, but Iran's Intelligence Minister Gholam Hossein Mohseni Ejehi said Tuesday that the initial investigation of Saberi was done by an expert on security and counterespionage at the Intelligence Ministry before her case was referred to the court.

An Iranian investigative judge involved in the case also alleged that Saberi was passing classified information to US intelligence services.

Islamic revolution

The US broke off diplomatic relations with Iran after the 1979 Islamic revolution and the take-over of the US embassy in Tehran by hard-line Iranian students. The Obama administration has said it is working with Swiss intermediaries who represent US interests in Iran to secure her release.

Saberi's parents have travelled to Iran from their home in Fargo in a bid to help win their daughter's release. Her father has said his daughter, who was Miss North Dakota in 1997, had been working on a book about the culture and people of Iran, and hoped to finish it and return to the US this year.