Pakistan opposition leader Benazir Bhutto was assassinated by a suicide bomber on Thursday, plunging the nuclear-armed country into chaos ahead of a general election she hoped to win.
Her death triggered a wave of anger in her native Sindh province, where she enjoyed huge popular support. In its capital, Karachi, angry crowds started fires and fired shots.
She has been martyred, said party official Rehman Malik.
Bhutto, 54, was assassinated as she left an election rally in the city of Rawalpindi and died in hospital. Police said the attacker fired shots at Bhutto before blowing himself up.
The attack brought widespread condemnation from around the world.
The United States, which sees Pakistan as a key ally in its battle against al Qaeda, had championed Bhutto as a popular leader who might help return the country to a civilian-led democracy after nearly a decade of military rule.
The United States strongly condemns this cowardly act by murderous extremists who are trying to undermine Pakistan's democracy, President George W. Bush said in a statement.
He urged Pakistanis to honor Bhutto's memory by continuing with the democratic process.
Bhutto, who inherited the political dynasty started by her father Zulfikar Ali Bhutto -- who was hanged in 1979 after a military coup -- had hoped to win an election set for January 8, giving her a chance to become prime minister for the third time.
It is the act of those who want Pakistan to disintegrate because she was a symbol of unity, said Farzana Raja, a senior official from Bhutto's Pakistan People's Party.
They have finished the Bhutto family. They are enemies of Pakistan.
POLICE ON RED ALERT
Paramilitary forces were put on red alert across the country to clamp down on any violence following Bhutto's death.
In Sindh, the family stronghold where the Oxford- and Harvard-educated Bhutto had a huge following, mainly amongst the poor, police said they were patrolling all towns and cities.
There is trouble almost everywhere, a senior police official said.
People cried and hugged each other outside the hospital where she died in Rawalpindi, a garrison city which is home to the Pakistan army.
Some shouted slogans against President Pervez Musharraf, who seized power in a military coup in 1999 but has since stepped down from the army.
Bhutto's main political rival, former prime minister Nawaz Sharif, told the crowd he was as upset as them. My heart is bleeding and I'm as grieved as you are.
Musharraf condemned in strongest possible terms the terrorist attack that resulted in the tragic death of Bhutto and many other innocent Pakistanis, the state news agency said.
It was not immediately clear whether Musharraf could decide to postpone the election and reimpose a state of emergency that was only lifted on December 15 after six weeks.
It is fair to assume now that elections cannot go ahead, said Dr Farzana Shaikh, an expert on Pakistan and an associate fellow at the Chatham House analysis group in London.
The electoral process has been stopped dead in its tracks. I think there is a very real possibility that Musharraf will decide that the situation has got out of control and that he needs to impose emergency rule again.
Police said 16 people had been killed in the attack on Bhutto. The man first fired at Bhutto's vehicle. She ducked and then he blew himself up, said police officer Mohammad Shahid.
It was the second attack on Bhutto in under three months. On October 19 a suicide bomber killed nearly 150 people as she paraded through Karachi on her return from eight years in exile.
On Thursday, Bhutto had told of the risks she faced.
I put my life in danger and came here because I feel this country is in danger. People are worried. We will bring the country out of this crisis, Bhutto told the Rawalpindi rally.
India, Pakistan's giant neighbor and rival, said Bhutto's assassination was a terrible blow to the democratic process.
In her death the subcontinent has lost an outstanding leader who worked for democracy and reconciliation in her country, said a spokesman for Prime Minister Manmohan Singh.
Bhutto became the first female prime minister in the Muslim world when she was elected in 1988 at the age of 35. She was deposed in 1990, re-elected in 1993, and ousted again in 1996 amid charges of corruption and mismanagement.
She said the charges were politically motivated.
Bhutto's family is no stranger to violence.
Apart from her father's execution, both of her brothers died in mysterious circumstances and she had said al Qaeda assassins tried to kill her several times in the 1990s.