Pakistani opposition leader Benazir Bhutto was freed from house arrest late on Friday, hours after she was stopped from leaving her Islamabad home to lead a rally against the president's imposition of emergency rule.

The detention order has been withdrawn, said Aamir Ali Ahmed, Acting Deputy Commissioner of Islamabad.

Earlier in the day police prevented Bhutto from leaving her home and sealed off the capital and the nearby city of Rawalpindi to stop a rally against President Pervez Musharraf.

Bhutto, the politician most capable of galvanizing mass protests against Musharraf's imposition of emergency rule, appealed to police to let her through their cordon.

The government has been paralyzed, Bhutto shouted to supporters across a barbed-wire barricade.

If he restores the constitution, takes off his uniform, gives up the office of the chief of army staff and announces an election by January 15, then it's okay, she said, vowing defiance if Musharraf did not comply.

Musharraf, who took power in a bloodless 1999 coup, said on Thursday elections would be held by February 15, about a month later than they were due.

He also said he would quit as army chief and be sworn in as a civilian president once new judges appointed to the Supreme Court struck down challenges against his re-election.

It remains to be seen whether Musharraf, who had viewed Bhutto as a potential ally, can control events set in train by his shock decision last Saturday to impose emergency rule and suspend the constitution.

RELEASE JUDGES

He has sacked most of the country's judges, putting senior officials -- including former chief Justice Iftikhar Chaudhry -- under house arrest, and ordered police to round up the majority of the opposition leadership and anyone else deemed troublesome.

The White House said earlier on Friday it remained concerned about the continued state of emergency and curtailment of basic freedoms in Pakistan.

Former prime minister (Benazir) Bhutto and other political party members must be permitted freedom of movement and all protesters released, said Gordon Johndroe, spokesman for the White House National Security Council.

An Interior Ministry spokesman said 2,500 people had been detained since the emergency was declared at the weekend, though Bhutto's Pakistan Peoples' Party say 5,000 of their activists have been picked up in the past couple of days.

Police fired tear gas to disperse protesters in Rawalpindi, where Bhutto planned to lead a rally. Barbed-wire barricades were erected on all roads leading to the venue.

A suicide bomb attack killed 139 people at a procession in Karachi to welcome Bhutto's return to Pakistan after eight years of self-imposed exile on October 18.

The government blamed Islamist militants angry at her backing of Musharraf's alliance with the United States.

Bhutto has also planned a motorcade from Lahore on November 13 as part of a mass agitation.

U.S. WORRIED

Under fire from Western allies and the international community, and with an angry Bhutto on his doorstep, Musharraf has become increasingly isolated, fuelling concern about instability in nuclear-armed Pakistan.

The concern I have is that the longer the internal problems continue, the more distracted the Pakistani army and security services will be in terms of the internal situation rather than focusing on the terrorist threat in the frontier area, U.S. Defense Secretary Robert Gates said on Friday.

A suspected suicide blast at the home of Political Affairs Minister Amir Muqam in the northwestern city of Peshawar killed three people on Friday, state-run Pakistan Television said. The minister was unhurt.

Police had earlier wielded batons and fired teargas to disperse hundreds of opposition protesters in Peshawar and a nearby town on Friday, police and witnesses said.

(Additional reporting Augustine Anthony, Zeeshan Haider and Robert Birsel; writing by Simon Cameron-Moore; editing by Tim Pearce)

Pakistan