Police swept the Pakistani capital on Saturday to arrest the leaders of opposition parties vowing to obstruct President Gen. Pervez Musharraf's re-election bid, officials said.

Security officials said police in Islamabad had orders to take some 35 opposition leaders into preventive custody.

The party of exiled former Prime Minister Nawaz Sharif and a coalition of Islamist parties that deplores Musharraf's alliance with the United States were targeted.

Police served a warrant on Javed Hashmi, acting president of Sharif's Pakistan Muslim league-N, at a block of apartments for lawmakers in the government district.

The warrant said he would be jailed for 30 days to stop him from making inflammatory speeches at protests where "miscreants" could "cause disruption and acts of sabotage and terrorism."

Hashmi, who was not immediately led away, said Musharraf's Western backers should press the military-led government to uphold the same democratic standards that they enjoy.

"They are ruling the country with the gun in hand," Hashmi told an Associated Press reporter at his apartment, where four armed police stood guard outside. "They think that the (military) uniform, not the people of Pakistan, are the source of power."

Several police vehicles were seen leaving the apartment block at about midnight Saturday. Hashmi said at least 15 other opposition politicians were detained.

Deputies of Sharif, who was ousted in Musharraf's 1999 coup, along with religious parties are spearheading opposition to the general's plan to ask for a new five-year term in a ballot of federal and provincial lawmakers on Oct. 6.

The ruling Pakistan Muslim League-Q party nominated Musharraf after he offered this past week to quit as army chief if he wins another term as head of state.

On Friday, the opposition alliance vowed that their legislators would resign from the assemblies a week before the presidential vote to deny it legitimacy.

The parties, who have also asked the Supreme Court to declare Musharraf ineligible to run for another presidential term, also pledged to mount street protests. Anti-Musharraf lawyers said they would blockade the Election Commission to prevent the general from filing his nomination papers.

A senior police official said authorities had reacted by issuing warrants for the arrest of 35 opposition party leaders. An intelligence official said the move was in response to the threat to escalate the confrontation with the government and disrupt the election.

Both officials spoke to AP on condition of anonymity because they are not authorized to speak on the record.

Federal and city government officials could not be reached for comment.

Prime Minister Shaukat Aziz urged lawmakers to back the president, a government statement said Saturday.

On Friday, Aziz told Cabinet ministers at his office that Musharraf's re-election "will auger well for the stability, progress and prosperity of Pakistan and move the country further on the path of democracy," the statement said.

Musharraf's popularity and his power have eroded since his botched effort to fire the Supreme Court's chief justice earlier this year. His administration is also struggling to contain a surge in Islamic militancy.

Underscoring the threat, al-Qaida leader Osama bin Laden urged Pakistanis to rebel against Musharraf in a message released Thursday.

Musharraf has called for moderate political forces in Pakistan to unite to defeat extremism and has held talks on a possible power-sharing deal with former Prime Minister Benazir Bhutto, a liberal vowing to return home Oct. 18 after eight years of self-exile.

Bhutto has also threatened to withdraw her lawmakers from Parliament if Musharraf doesn't compromise, for instance by lifting a ban on her serving a third term as prime minister, but is keen to avoid a political showdown that could destabilize the country.

Saturday's sweep mirrored the tactics used to ensure no crowds turned out to welcome Sharif when he tried to return from exile on Sept. 10. Hundreds of opposition activists were briefly jailed to prevent them reaching Islamabad airport, from where Sharif was swiftly expelled to Saudi Arabia.

Hafiz Hussain Ahmad, a leader of the pro-Taliban Jamiat Ulema-e-Islam party, said police had detained him at his residence. He said it was unclear whether he would be confined there or taken away.

"This government will do anything to clear the way for the presidential election," he told AP. "They are using the state machinery to curb the opposition."