U.S. Secretary of State Condoleezza Rice has called for Iran to release an Iranian-American academic accused of "crimes against national security."

Ms. Rice told reporters in Moscow that the detainment of scholar Haleh Esfandiari "underscores the nature of the Iranian regime." She said Ms. Esfandiari ought to be released immediately.

Earlier Tuesday, a spokesman for Iran's judiciary, Ali Reza Jamshidi, said Ms. Esfandiari has been detained under the authority of the Intelligence Ministry.

Esfandiari, who has dual U.S.-Iranian citizenship, is the director of the Middle East program at Washington's Woodrow Wilson International Center for Scholars.

The center says Iranian authorities have prevented her from leaving the country since December and that she is currently in Tehran's Evin prison. A hardline Iranian newspaper Kayhan has accused the academic of spying for the U.S. and Israel.

Last week, the United States urged Iran to release the academic as well as two other detained Iranian-American women.

One of them is Parnaz Azima, a correspondent for U.S.-funded Persian language broadcaster Radio Farda. She has been prevented from leaving Iran since January.

Both Esfandiari and Azima were in Iran to visit their mothers.

The identity of the third woman has not been disclosed at the request of her family.

The United States and Iran have not had diplomatic relations since 1980.

Some information for this report was provided by AFP and AP.