More than 20 civil liberties and other groups had invoked the US Freedom of Information Act, a law that allows the disclosure of certain government records, to challenge the secret arrests.

The court said the government could keep secret the names of more than 700 individuals detained for immigration violations and those arrested as material witnesses in the investigation into the September 11 attacks.

The court accepted the justice department's argument that revealing the identities of those detained might help Osama bin Laden's al-Qaida network.