Former Pakistani prime minister Benazir Bhutto wasgunned down Thursday by an attacker who then blew himself up, killing at least 20 others.

The assassination of Bhutto sparked riots across the country, with at leastsix people reported killed in the ensuing violence.

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Supporters of Pakistani opposition leader Benazir Bhutto carry her coffin after her body was released from the hospital in Rawalpindi on Thursday. ((Farooq Naeem/AFP/Getty Images))

Bhutto had just finished addressing thousands of supporters in the garrison city of Rawalpindi, about 18 kilometres south of Islamabad, when a man stepped from the crowd and fired. Bhutto was hit in the neck and chest.

The killer then blew himself up.

Bhutto died around 6:16 p.m. local time (8:16 a.m. ET) at Rawalpindi General Hospital after undergoing emergency surgery.

Her body has been flown to the southern Pakistani province of Sindh, where she'll be buried in thefamily graveyard alongside her father, Zulfikar Ali Bhutto, on Friday.

In a brief televised address, Pakistani President Pervez Musharraf condemned the attack and announced three days of mourning for Bhutto. Duringthat time,all schools, commercial centres and banks will remain closed.

Meanwhile, paramilitary forces were put on "red alert" across the country, Reuters reported.

"This cruelty is the work of those terrorists with whom we are fighting," Musharraf said.

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Afghan President Hamid Karzai, right, walks with former Pakistani prime minister Benazir Bhutto after a meeting at a hotel in Islamabad on Thursday, hours before her assassination in Rawalpindi. ((Farooq Naeem/AFP/Getty Images))

Bhutto escaped an assassination attempt in October when twin explosions ripped through crowds in Karachi welcoming her home from eight years of exile. Nearly 150 people died in the attacks.

One of the doctorswhoattended to Bhutto said she had a bullet in the back ofher neck that damaged her spinal cord before it exited fromthe side of her head.

Another bullet pierced the back ofBhutto's shoulder and came out through her chest, the doctors said on condition of anonymity because he was not authorized to speak to the media.

Bhutto was given an open-heart massage, but the main cause of death was damage to her spinal cord, he said.

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Rawalpindi, a garrison city, is about 15 kilometres south of the capital, Islamabad. ((CBC))

Upon hearing reports of her death, thousands of Bhutto's supporters gathered outside the hospital in Rawalpindi chanting "Dog, Musharraf, dog."

Violence erupts in at least 6 cities

Hours after Thursday's attack, gunfire was heardand smoke rose above Karachi, Bhutto's hometown, CBC producer Habiba Nosheen reported from the city about 1,300 kilometres southwest of Islamabad.

Angry demonstrators reportedly burned a local hospital, a gas station and numerous vehicles, she said, while about 250 protesters had occupied a police station in the southern coastal city.

"The roads have been closed off," Nosheen said. "People are staying inside their homes."

Protesters have also set fire to tires on the roads,and gunmenshotand wounded two police officers,according to Fayyaz Leghri, a local police official.

Violence alsobroke out in Lahore, Multan and Peshawar, where Bhutto's supporters burned banks, state-run grocery stores and private shops. Others set fire to election offices for the ruling party, according to Pakistani media.

In Tando Allahyar, 190 kilometres north of Karachi,one man was killed in a shootout between police and protesters, said Mayor Kanwar Naveed. And in the nearby townTando Jam, protesters forced passengers to get out of a train and then set it on fire.

Sharif calls for Musharraf's resignation

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A supporter of Benazir Bhutto's party cries as he sits among bodies after the bomb blast Thursday in Rawalpindi. ((Aamir Qureshi/AFP/Getty Images))

The assassination drew immediate and widespread condemnation from world leaders and cast doubt over whether Pakistan's upcoming parliamentary elections would be held.

The Western-educated Bhutto enjoyed high popularity at home and abroad, and was leading Pakistan's largest political party heading into the Jan. 8 vote.

Bhutto's chief rival, former prime minister Nawaz Sharif, announced his party would boycott the election following the assassination.

Sharif also said Musharraf was "the root cause of all problems" in Pakistan and should resign immediately.

"The holding of fair and free elections is not possible in the presence of Pervez Musharraf," said the former prime minister, who was ousted by Musharraf in a 1999 coup.

Earlier, Sharif told the BBC that Bhutto's death was a tragedy for "the entire nation."

Security requests ignored: adviser

Questions were immediately raised about how a suicide bomber could get so close to Bhutto after previous attacks.

Many observers were left to speculate whether Musharraf's government or Pakistan's security forces were involved in the attack, said Tariq Amin-Khan, an assistant professor of politics and public administration at Toronto's Ryerson University.

"Security has been very lax," Amin-Khan told CBC News in a telephone interview from Karachi. "One could fault the government for what it has not done."

Musharraf himself has been the target of numerous attacks blamed on Islamist militants, who have reported ties with Pakistan's Inter-Services Intelligence Agency.

"I find it difficult to believe that Musharraf would be directly involved, but you can't put it past the security service agencies," Amin-Khan said.

Bhutto's security adviser also said the government had ignored requests for beefed-up security, including bomb-jammers, which can thwart signals sent to detonate explosives.

"We repeatedly informed the government to provide her proper security and appropriate equipment including jammers, but they paid no heed to our requests," Malik said.

Observers said Bhutto's death would spark fierce protests in a country where political bloodshed is common.

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Angry Pakistani supporters of Benazir Bhutto set buses ablaze in Lahore on Thursday following Bhutto's assasination. ((Arif Ali/AFP/Getty Images))

"All of Pakistan is in danger now," said Ibrahim Daniyal, secretary of the Pakistan Peoples Party of Canada's ad hoc committee. "You will see lots of riots … lots of blood."

The 54-year-old Bhutto, eldest daughter of former prime minister Zulfikar Ali Bhutto, served two terms as prime minister of Pakistan.

She went to the United States in 1969 to attend Radcliffe College in Massachusetts, then Harvard University and England, where she studied philosophy, politics and economics at Oxford.

After her studies, she returned to Pakistan where her father was charged with conspiring to commit a political murder and executed in 1979.

Bhutto was placed under house arrest for five years shortly before her father's execution, and then went to Britain where she became leader-in-exile of the Pakistan Peoples Party (PPP).

Coalition government

After Bhutto's return to Pakistan in 1988, the PPP won 39 per cent of the popular vote and she was sworn in as prime minister in a coalition government.

She was deposed 20 months later on allegations of corruption, but was re-elected again in 1993, only to be sacked in 1996 on similar charges.

Meanwhile, onThursday, four people were killed during a gun battle between pro-government supporters and Sharif's backers at a rally outside Pakistan's capital, Islamabad.

A spokesman for the party said Sharif was about two kilometres away when pro-government party supporters opened fire.

On Dec. 15, Musharraf ended a month-long state of emergency that saw crackdowns on opposition supporters, independent media and the purging of independent judges from the country's Supreme Court.

With files from the Associated Press