With al-Qa'ida claiming responsibility for a murder that has provoked the most serious crisis in the 60-year history of the nuclear-armed country, President Pervez Musharraf was under intense pressure from Washington to ensure Pakistan returned to democracy through elections scheduled for January 8.
But Mr Musharraf, who has become a key ally in the war on terror, was facing a furious backlash from his own people, with mobs chanting "Killer Musharraf, go" as they set fire togovernment offices, shops and cars.
At least 19 were killed and scores wounded as police and paramilitary forces opened fire in an attempt to halt the violence that has engulfed Pakistan since the murder of Ms Bhutto on Thursday night.
Despite al-Qa'ida claiming the assassination was carried out on the orders of Ayman al-Zawahiri, Osama bin Laden's second-in-command, much of the anger was directed at Pakistan's military-backed ruler.
Demonstrators blamed Mr Musharraf and the army for failing to provide sufficient security to prevent a lone assassin first launching a gun attack and then triggering a suicide bomb as Ms Bhutto campaigned in the garrison city of Rawalpindi, home to the headquarters of Pakistan's military.
Analysts say Mr Musharraf is unlikely to have ordered the killing, but elements of the army and intelligence service, the ISI, stood to lose power if she became prime minister for a third time.
Anger intensified last night when it emerged that Ms Bhutto, 54, had two months ago sent an email to a US adviser saying that if she were killed, Mr Musharraf would have to bear some of theblame. "Nothing will, God willing, happen," she wrote to Mark Siegel, her US spokesman, "Just wanted u to know if it does ... I would hold Musharaf (sic) responsible."
Mr Musharraf was insistent that the blame for the killing lay with Islamic extremists opposed to Ms Bhutto's pro-Western stance. "This brutality is the handiwork of those terrorists against whom we are fighting," he said as he declared three days of national mourning.
But members of Ms Bhutto's Pakistan People's Party claimed electronic jamming equipment provided by the Government to prevent a suicide attack had proved faulty and evidence from the murder scene had been lost after government agents ordered the area be washed clean.
Political scientist Rasul Baksh Rais, of Lahore University, described the assassination as "the most serious setback for democracy in Pakistan".
"Musharraf's main concern now will be to maintain law and order and make sure this does not turn into a major movement against him," he said.
Last night, however, there were indications that was happening. "People are on the streets everywhere smashing things up. There's trouble all over Pakistan," a senior police officer said.
As troops were issued with orders to shoot protesters on sight and a revenge bomb attack left four of Mr Musharraf's supporters dead, Ms Bhutto's body was borne in a simple wooden coffin to her family home at Naudero, deep in the agricultural interior of the southern Sindh province.