In what could be one of the biggest counterterrorism seizures in US history, federal prosecutors sought to take over four US mosques and a New York City skyscraper owned by a Muslim organization suspected of being controlled by the Iranian government. Prosecutors on Thursday filed a civil complaint in federal court against the Alavi Foundation, seeking the forfeiture of more than $500 million in assets. The assets include bank accounts; Islamic centers consisting of schools and mosques in New York, Maryland, California and Houston; more than 100 acres (40 hectares) in Virginia; and a 36-story Manhattan office tower. Confiscating the properties would be a sharp blow against Iran, which the US government has accused of bankrolling terrorism and trying to build a nuclear bomb. A telephone call and e-mail to Iran's U.N. Mission seeking comment were not immediately answered. John D. Winter, the Alavi Foundation's lawyer, said it intends to litigate the case and prevail. He said the foundation has been cooperating with the government's investigation for the better part of a year. "Obviously the foundation is disappointed that the government has decided to bring this action," Winter told The Associated Press. It is extremely rare for US law enforcement authorities to seize a house of worship, a step fraught with questions about the First Amendment right to freedom of religion. The action against the Shiite Muslim mosques is sure to inflame relations between the US government and American Muslims, many of whom fear a backlash after last week's Fort Hood shooting rampage, blamed on a Muslim American major. "Whatever the details of the government's case against the owners of the mosques, as a civil rights organization we are concerned that the seizure of American houses of worship could have a chilling effect on the religious freedom of citizens of all faiths and may send a negative message to Muslims worldwide," said Ibrahim Hooper, spokesman for the Council on American-Islamic Relations. It is unclear what will happen to the properties if the government ultimately prevails. But the government typically sells properties it seizes through forfeiture and sometimes distributes the money to crime victims. US attorney's office spokeswoman Yusill Scribner said there are no allegations of any wrongdoing on the part of the tenants or occupants of the properties, which will remain open. Prosecutors said the Alavi Foundation managed the office tower on behalf of the Iranian government and, working with a front company known as Assa Corp., illegally funneled millions in rental income to Iran's state-owned Bank Melli. A US Treasury official has accused Bank Melli of providing support for Iran's nuclear program, and it is illegal in the United States to do business with the bank. US officials have long suspected the foundation was an arm of the Iranian government. A 97-page complaint details involvement in foundation business by several top Iranian officials, including the deputy prime minister and ambassadors to the United Nations. "For two decades, the Alavi Foundation's affairs have been directed by various Iranian officials, including Iranian ambassadors to the United Nations, in violation of a series of American laws," US Attorney Preet Bharara said in a statement. There were no raids as part of the forfeiture action Thursday. The government is simply required to post notices of the civil complaint on the properties. As prosecutors outlined their allegations against Alavi, the Islamic centers and the schools they run carried on with normal activity. The mosques' leaders had no immediate comment. Parents lined up in their cars to pick up their children at the schools within the Islamic Education Center of Greater Houston and the Islamic Education Center in Rockville, Maryland, No notices of the forfeiture action were posted at either place as of late Thursday. At the Islamic Institute of New York, a mosque and school in Queens, two US marshals rang a doorbell repeatedly, taped a forfeiture notice to the window and left a large document on the ground. A group of men came out and took the document after the marshals left. The fourth Islamic center marked for seizure is in Carmichael, California. The skyscraper, known as the Piaget building, was erected in the 1970s under the shah of Iran, who was overthrown in 1979. Tenants include law and investment firms and other businesses. The building, last valued in 2007 at $570 million to $650 million, has been an important source of income for the foundation over the past 36 years. Tax records show the foundation earned $4.5 million from rents in 2007. That money helps fund the centers and other ventures, such as sending educational literature to imprisoned Muslims in the US The foundation also has invested in dozens of mosques around the country and supported Iranian academics at prominent universities. If prosecutors seize the skyscraper, the foundation would have almost no way to continue supporting the Islamic centers, which house schools and mosques. That could leave a major void in Shiite communities, and hard feelings toward the FBI, which played a big role in the investigation. The forfeiture action comes at a tense moment in US-Iranian relations, with the two sides at odds over Iran's nuclear program and its arrest of three American hikers. But Michael Rubin, an expert on Iran at the American Enterprise Institute, said the timing was probably coincidental and not an effort to influence Iran on those issues. "Suspicion about the Alavi Foundation transcends three administrations," Rubin said. "It's taken ages dealing with the nuts and bolts of the investigation. It's not the type of investigation which is part of any larger strategy." Legal scholars said they know of only a few previous cases in which law enforcement authorities have seized a house of worship. Marc Stern, a religious-liberty expert with the American Jewish Congress, called such cases extremely rare. The Alavi Foundation is the successor organization to the Pahlavi Foundation, a nonprofit group the shah used to advance Iran's charitable interests in America. But authorities said its agenda changed after the fall of the shah. In 2007, the United States accused Bank Melli of providing services to Iran's nuclear and ballistic missile programs and put the bank on its list of companies whose assets must be frozen. Washington has imposed sanctions against various other Iranian businesses.