At least 20 others were killed in the attack on the rally for Jan. 8 parliamentary elections where the 54-year-old former prime minister had just spoken.
At least five people were killed across the country in rioting that broke out in the aftermath of the assassination. In the southern port city of Karachi, angry Bhutto supporters shot at police and burned a gas station.
At the hospital where Bhutto died, some supporters smashed glass and wailed, chanting slogans against President Pervez Musharraf. Musharraf blamed Islamic extremists for her death and said he would redouble his efforts to fight them.
"This is the work of those terrorists with whom we are engaged in war," he said in a nationally televised speech. "I have been saying that the nation faces the greatest threats from these terrorists. ... We will not rest until we eliminate these terrorists and root them out."
In the U.S., a tense looking President Bush "by murderous extremists who are trying to undermine Pakistan's democracy." White House spokesman Scott Stanzel said Bush spoke briefly by phone with Musharraf.
Musharraf convened an emergency meeting with his senior staff, where they were expected to discuss whether to postpone the elections, an official at the Interior Ministry said, speaking on condition of anonymity because of the sensitivity of the talks. Analysts say Bhutto could have commanded around 26 percent of the popular vote in the elections, reports CBS News correspondent Sheila MacVicar.
CBS News correspondent Richard Roth reports that a claim for the killing has come from al Qaeda, but a feeling that Musharraf's government shares the blame for Bhutto's death, whoever pulled the trigger, is widespread among her followers who make up the country's biggest political party.
The government announced three days of mourning for Bhutto, including the closing of schools, commercial centers and banks.
Nawaz Sharif, another former prime minister and leader of a rival opposition party, demanded Musharraf resign immediately and announced his party would boycott the upcoming election.
The attacker struck just minutes after Bhutto addressed thousands of supporters in the Rawalpindi, a city 8 miles south of Islamabad where the army is headquartered. She was shot in the neck and chest by the attacker, who then blew himself up, said Rehman Malik, Bhutto's security adviser.
Sardar Qamar Hayyat, a leader from Bhutto's party, said at the time of the attack he was standing about 10 yards away from her vehicle - a white, bulletproof SUV with a sunroof.
"She was inside the vehicle and was coming out from the gate after addressing the rally when some of the youths started chanting slogans in her favor. Then I saw a smiling Bhutto emerging from the vehicle's roof and responding to their slogans," he said.
"Then I saw a thin, young man jumping toward her vehicle from the back and opening fire. Moments later, I saw her speeding vehicle going away," he added.
"Mangled bodies lay in a pool of blood and pieces of clothing and shoes were scattered on the road. The clothing of some victims was shredded and people covered their bodies with party flags.
There was an acrid smell of explosive fumes in the air.
Police cordoned off the street and rescuers rushed to put victims in ambulances as onlookers wailed nearby.
Bhutto was rushed to the hospital and taken into emergency surgery. She died about an hour after the attack.
Hours later, her body was carried out of the hospital in a plain wooden coffin by a crowd of supporters. Her body was expected to be transferred to an air base and brought to her hometown of Larkana.
A doctor on the team that treated her said she had a bullet in the back of the neck that damaged her spinal cord before exiting from the side of her head. Another bullet pierced the back of her shoulder and came out through her chest.
She was given open heart massage, but the main cause of death was damage to her spinal cord, he said on condition of anonymity because he was not authorized to speak to the media.
"At 6:16 p.m., she expired," said Wasif Ali Khan, a member of Bhutto's party who was at Rawalpindi General Hospital.
"The surgeons confirmed that she has been martyred," Bhutto's lawyer Babar Awan said.
Bhutto's supporters at the hospital exploded in anger, smashing the glass door at the main entrance of the emergency unit. Others burst into tears. One man with a flag of Bhutto's Pakistan People's Party tied around his head was beating his chest.
"I saw her with my own eyes sitting in a vehicle after addressing the rally. Then, I heard an explosion," Tahir Mahmood, 55, said sobbing. "I am in shock. I cannot believe that she is dead."
Many chanted slogans against Musharraf, accusing him of complicity in her killing.
"We repeatedly informed the government to provide her proper security and appropriate equipment including jammers, but they paid no heed to our requests," said Malik, the security adviser.
As news of her death spread, angry supporters took to the streets.
In Karachi, shop owners quickly closed their businesses as protesters set tires on fire on the roads, torched several vehicles and burned a gas station, said Fayyaz Leghri, a local police official. Gunmen shot and wounded two police officers, he said.