In an "unprecedented" move which may have wide ramifications, US federal authorities have taken legal steps to seize four mosques and a 36-storey Manhattan skyscraper owned by a Muslim organisation long suspected of having links with the Iranian government.

Prosecutors filed a civil complaint in federal court seeking forfeiture of more than USD 500 million in assets of the Alavi Foundation and an alleged front company, in what could turn out to be one of the biggest counter-terrorism seizures in the US history.

The Foundation, which describes itself as a non-profit organisation, was not immediately available for comments.

Properties targeted are the Islamic Education Centre of Greater Houston, Islamic centres in New York City, Maryland and California, more than 100 acres in Virginia and the 36-story office tower called Piaget building on Fifth Avenue in New York. The Islamic centres house mosques and schools.

"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.

"As today's complaint alleges in great detail, the Alavi Foundation has effectively been a front for the government of Iran," he said.

Criticising the move, he Council on American-Islamic Relations (CAIR) said a government effort to seize mosques was "unprecedented" and likely to have First Amendment implications.

"Whatever the details of the government's case against the owners of the mosques, as a civil rights organisation 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," CAIR spokesman Ibrahim Hooper said.

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