TEHRAN, Iran - Iran officially confirmed Sunday that it is holding an Iranian-American peace activist, the fourth dual citizen the country has detained in recent months.

In this undated photo released by the Center for Citizen Peacebuilding, Ali Shakeri of Lake Forest, Calif., is shown. Iran confirmed Friday, June 8, 2007, that it is holding the Iranian-American peace activist, the fourth dual citizen it has detained in recent months, according to the Iranian Student News Agency. [AP]

Mohammad Ali Hosseini, the spokesman for Iran's foreign ministry, confirmed at his weekly news briefing that Iranian-American Ali Shakeri had been detained.

On Friday, the semi-official ISNA news agency had first reported that Shakeri of Lake Forest, Calif., was being held and investigated by the security department of the Tehran prosecutor's office.

At the briefing, Hosseini also reiterated that Iran has no information about a former FBI agent, Robert Levinson, who the United States says has been missing since March after traveling to an Iranian resort island on private business.

"In a meeting with the Swiss ambassador, we reminded them that we have not found any information about him (Levinson)," Hosseini said when asked about the former FBI agent.

The Swiss Embassy handles US interests in Iran because the United States and Iran do not have formal diplomatic ties.

At his briefing, Hosseini also accused the United States of using scientific and research cooperation as a guise to work against Iran. It was not clear what he referred to, but many academics have criticized Iran for arresting scholars.

The US State Department has said Shakeri, a founding board member of the University of California, Irvine, Center for Citizen Peacebuilding was supposed to have left Iran for Europe on May 13 but never arrived.

Iranian officials previously have confirmed the detentions of three other Iranian-Americans: scholar Haleh Esfandiari, who is the director of the Middle East program at the Woodrow Wilson International Center for Scholars; Kian Tajbakhsh, an urban planning consultant with George Soros' Open Society Institute; and journalist Parnaz Azima, who works for US funded-Radio Farda.

All three have been accused of endangering Iran's national security and of espionage, according to a judiciary spokesman.

It is not known if Shakeri has been accused of specific wrongdoing.

All were in Iran visiting family members or engaged in professional work, according to the US State Department and their relatives and employers.

President Bush has demanded that Iran "immediately and unconditionally" release those held, and has denied that they were spying for the US.

Family, colleagues and employers also have denied the allegations.

Bush's remarks drew sharp criticism from Iranian officials. Earlier this week, Iran accused Bush of interfering in the country's internal affairs.

Iran in recent weeks has escalated accusations against the US, saying it has uncovered spy rings organized by the US and its Western allies.