ISLAMABAD, Pakistan — Opposition leader Benazir Bhutto's assassination deals a stunning blow to liberal political forces in Pakistan and gathering unrest by her supporters risks tipping the volatile country into chaos.

Her killing also quashes hopes of Western governments that the charismatic, two-time former prime minister could team up with President Pervez Musharraf and galvanize Pakistan's fight against Taliban and al-Qaida militants after Jan. 8 elections.

"This assassination is the most serious setback for democracy in Pakistan," said Rasul Baksh Rais, a political scientist at Lahore's University of Management Sciences. "It shows extremists are powerful enough to disrupt the democratic process. Musharraf's major concern now will be to maintain law and order and make sure this does not turn into a major movement against him."

Prime Minister Mohammedmian Soomro said today the government had no immediate plan to postpone the parliamentary elections, despite a top opposition leader's decision to boycott the poll.

"Right now the elections stand where they were," he told a news conference. "We will consult all the political parties to take any decision about it."

Bhutto died Thursday when an attacker shot her and then blew himself up as she left a political rally in Rawalpindi, a city near the capital where Pakistan's army has its headquarters. It was the second suicide attack against her since her tumultuous homecoming from an eight-year exile in October.

The other key opposition leader, Nawaz Sharif — whose government was ousted in the 1999 coup that brought Musharraf to power — quickly announced he was boycotting the parliamentary elections, which are meant to usher Pakistan toward civilian government after years of military dominance.

Talat Masood, a retired general and now a political analyst, expected Bhutto's party to follow suit — a move that would rob the vote of legitimacy.

Bhutto had accused elements in the ruling party of backing militants to kill her — claims that could gain more traction now despite government denials.

At the very least, the government will appear to be losing its grip over Pakistan.

"Conditions in the country have reached a point where it is too dangerous for political parties to operate," Masood said.

He anticipated that Musharraf, who recently suspended the constitution for six weeks, could take drastic steps.

But Musharraf, who was himself targeted twice in Rawalpindi by al-Qaida bombers in December 2003, gave no immediate sign of an authoritarian backlash to Bhutto's assassination. He declared three days of national mourning and vowed to fight the terrorists behind her killing.

Only a few months ago, he held direct talks with Bhutto and paved the way for her return from exile.

Anthony Cordesman at the Center for Strategic and International Studies in Washington, warned that any suspicion that Musharraf had a role in Bhutto's killing or knew about the plot and failed to prevent it could pitch Pakistan "to the edge of civil conflict."