Pakistani Prime Minister Shaukat Aziz Wednesday ordered the immediate withdrawal of a complaint against 200 journalists who protested against new regulations on the media.
The complaint stems from the journalists' rally in Islamabad on Monday, in defiance of a two-month ban on demonstrations in the capital.
Political opposition officials say authorities are cracking down on activists ahead of rallies planned for Thursday in Punjab province.
Spokespeople for two opposition parties - the Pakistan People's Party and the Pakistan Muslim League - say hundreds of their workers have been detained. The government confirms that about 300 people have been taken into custody. Officials have called it an effort to preserve law and order.
Anti-government protests are planned for Thursday to denounce recent curbs on the media and President Pervez Musharraf's suspension of Chief Justice Iftikhar Mohammed Chaudhry for alleged abuses of office.
On Monday, General Musharraf tightened media regulations amid growing dissent after his suspension of the Supreme Court chief justice.
General Musharraf had announced a series of amendments granting more powers to the country's media regulators, Pakistan Electronic Media Regulatory Authority.
The emergency law allows authorities to seize equipment, revoke licenses and seal the premises of broadcasters deemed to be operating illegally.
Some information for this report was provided by AFP and AP.