Teheran's imprisonment of a prominent American-Iranian academic illustrates the Iranian government's increasing fear that the US is using pro-democracy advocates to plot regime change against it, analysts say. Haleh Esfandiari, director of the Middle East Program at the Woodrow Wilson Center for Scholars, went to Iran on a personal visit to see her ailing mother last year. Now she is held in a notorious Iranian prison, her Washington-based institute said. Before her arrest on Tuesday, she was trapped in the country after masked men stole her luggage and passports as she tried to leave in December. In the intervening months, she was repeatedly interrogated by authorities for up to eight hours a day and questioned mainly on the activities of the Wilson Center, according to the organization. "There is a paranoia of people with ties to Iran coming from the US," said Jon B. Alterman, of the Washington Center for Strategic and International Studies. "The sad thing is that when you start accusing women like Esfandiari, you are grasping at straws." The 67-year-old Esfandiari, who has been living in the US since 1980, has for years brought prominent Iranians to Washington to talk about social change. Some have been detained and subsequently questioned back home because of "Iranian concerns about people talking openly about dramatic change in the country," Alterman said. Tehran officials have not said a word on Esfandiari - nor confirmed she is being held in Evin prison. 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 government is suspicious of consultancy groups, think tanks, there is a fear that these groups are mobilizing inside and outside the country for dissent," Mahan Abedin from the London-based Center for the Study of Terrorism, said. "Arrests such as this one are a heavy handed, sledgehammer approach to remove the threat." Hadi Ghaemi, an Iran expert for the New York-based Human Right Watch, said prominent Iranian activists abroad are now worried about making trips to their homeland. He told AP he has been "receiving questions and concerns from several scholars, filmmakers, and researchers who are re-evaluating the wisdom of their imminent trips to Iran." Ghaemi has not been to Iran for three years because Tehran refuses to allow Human Rights Watch into the country. He said authorities were aiming to force Esfandiari "to make false confessions to give credence to the state propaganda that the US is responsible for all forms of domestic dissent and criticism." Karim Sadjadpour, an expert on Iran at the Carnegie Endowment for International Peace in Washington, said some of the Iranian scholars and analysts Esfandiari had brought to the U.S. for visits in the past were sympathetic to the Iranian government. "By detaining her, the Iranian government only eliminates an advocate for diplomacy and strengthens the voices of those in Washington who say the regime is too cruel to be engaged," he said. 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 US Secretary of State Condoleeza Rice released US$85 million (â‚¬63 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. Abedin says that Iran "feels the need to hit back" after arrests or disappearances of Iranians elsewhere. In January, five Iranians were captured by US forces in a raid in northern Iraq. The US military has said the five were part of a Revolutionary Guard force providing money, weapons and training to Shiite militias in Iraq. Iran says they were engaged exclusively in consular work. In December, a retired former Iranian deputy defense minister went missing in Turkey. Ali Reza Asghari, 46, a retired Revolutionary Guard general, was on a private visit from Syria when he went missing. Turkish officials have said that it was likely Asghari was kidnapped by Western intelligence services. In April, Israel's Shin Bet security agency said it had broken up an Iranian plot to recruit Israelis of Iranian origin as spies. Israel Army Radio cited an unidentified senior Shin Bet officer as saying the agency uncovered 10 recruitment attempts in the past two years.