Washington - US Secretary of State Hillary Rodham Clinton called for the immediate release of an American journalist sentenced to eight years in prison in Iran on "baseless" espionage charges.

"We believe she should be freed immediately," Clinton said. "The charges against her are baseless."

Roxana Saberi had been held in Iran for months prior to last week's sentence. The Iranian government charges she was operating in the country illegally because she was not a credentialed journalist.

Saberi, 31, is a reporter for National Public Radio, a US government-funded broadcaster in the United States. She had originally faced less serious charges of buying alcohol and working without a valid press credential.

Iranian courts have sought to ensure Saberi will have the right to appeal the case, while Iranian leaders have urged the United States against politicizing the case.

In a suprising move, Iranian President Mahmoud Ahmadinejad on Sunday intervened in the case, calling on Tehran's general prosecutor Saaid Mortazavi to personally follow it with precision and fairness. He also stressed Saberi's right for legal defence assistance.

On Monday, Ayatollah Mahmoud Hashemi-Shahroudi, the head of Iran's judiciary, ordered the director general of the Tehran court to give Saberi all legal rights in the appeal court.

Observers considered Ahmadinejad's intervention as an effort by the government to persuade the judiciary to revise the harsh sentence and avoid another international political crisis. (dpa)