Although no arrests were made immediately, the move came a day after hundreds of journalists, lawyers and opposition supporters rallied in Islamabad to protest the imposition of an emergency ordinance by President Gen Pervez Musharraf that tightened the regulation of electronic media, including private TV channels that he has accused of anti-government bias.

In addition, more than 60 opposition activists have been detained in Lahore and five other cities in Punjab province since Monday on government orders to keep them from joining in journalists' protests and creating law-and-order problems, a senior Lahore police official said on condition of anonymity because he was not authorised to make media comments.

"I have talked to senior police officials but they are not telling me under what charges the action is being carried out," said Naveed Chaudhry, a spokesman for the opposition Pakistan Peoples Party.

Musharraf's new ordinance authorises the government to seal the premises of broadcasters or distributors breaking the law, and raises possible fines for violations from $16,665 to $166,650. An offender can also have its license suspended.

"This presidential decree is another brick in the wall of censorship that the government is building to shield itself at a time of political upheaval," said Joel Simon, executive director of the international media group Committee to Protect Journalists.

"We call on the government to rescind the decree immediately."