Iran's foreign ministry on Sunday confirmed the government had detained a prominent American-Iranian academic who traveled to the country in December to visit her 93-year-old mother.

The admission by ministry spokesman Mohammad Ali Hosseini came a day after the hard-line Iranian newspaper Kayhan accused Haleh Esfandiari of spying for the U.S. and Israel and for attempting to launch a democratic revolution in the country.

"She will be treated as other Iranian nationals," said Hosseini during his weekly press briefing. "It is natural if there is any problem, it will be handled by authorities."

Although Hosseini said Esfandiari's detention was "based on law," he did not provide further details on why the director of the Middle East Program at the Washington-based Woodrow Wilson Center for Scholars was being held.

The Kayhan newspaper was more explicit in its allegations against Esfandiari, who the Wilson Center has said was detained on Dec. 30 by three masked men with knives as she was on her way to the airport.

"She has been one of the main elements of Mossad in driving a velvet revolution strategy in Iran," the paper wrote. "She formed two networks, including Iranian activists, in the U.S and Dubai for toppling down (the Islamic government.)

The arrest came amid increasing restrictions on domestic non-governmental organizations — particularly women's rights groups — by the hard-line government of President Mahmoud Ahmadinejad.

Authorities have been tightening the reins as tensions have increased with the West over Iran's nuclear program and over the conflict in neighboring Iraq. Security officials often warn that Iran's enemies are using domestic critics to put pressure on the government.

The 67-year-old academic, who has been living in the U.S. since 1980, has for years brought prominent Iranians to Washington to talk about social change, some of whom have been detained and subsequently questioned back home.

Iranian leaders have stepped up their warnings since the U.S. increased its military presence in the Gulf earlier this year. Their suspicions have been further raised since U.S. Secretary of State Condoleezza Rice released $85 million to promote democratic institutions in Iran.

Other Iranian-Americans have also been prohibited from leaving Iran in recent months, including journalist Parnaz Azima, who works for the U.S.-funded Radio Farda. Another American, former FBI agent Robert Levinson, disappeared in March after going to Iran's resort island of Kish, and his whereabouts are unknown.