Benazir Bhutto was waving from the sunroof of her bullet-proof Land Cruiser when the assassin struck, first firing shots and then blowing himself up, mortally wounding Pakistan's former Prime Minister and opposition leader.

As rioting broke out across Pakistan last night, the exact cause of her death was still unclear, with some saying she died from shots to the head and neck and others saying the blast killed her.

What was certain was that Ms Bhutto was declared dead at 6.16pm local time in a hospital in the garrison town of Rawalpindi, plunging Pakistan into chaos and adding a new chapter to her family's tragic history.

Fittingly for a woman who pledged her life to Pakistani politics, she was killed after addressing her first election rally since she returned from eight years' self-imposed exile in October.

"I put my life in danger and came here because I feel this country is in danger," she told the rally. "We will bring the country out of this crisis."

Ms Bhutto (54) began her final day by meeting leaders of her Pakistan People's Party (PPP) to plan its campaign for parliamentary elections, scheduled for January 8 but now thrown into doubt.

Backed by the United States and Britain, she hoped to win and serve a third term as Prime Minister, restoring democratic rule after President Pervez Musharraf's resignation as army chief last month.

Tactics

After talking tactics with senior aides, she boarded her white Land Cruiser to travel from her villa in Islamabad to a meeting with President Hamid Karzai of Afghanistan at the end of his two-day visit to Pakistan.

Ms Bhutto told Mr Karzai that if elected again, she would work with him to fight the Taliban and al Qa'ida militants sheltering in northwestern Pakistan, who had repeatedly threatened to kill her.

She then went to Rawalpindi, an hour's drive away, to attend the rally despite repeated warnings that she was being targeted by suicide bombers.

She was all too aware the threats were genuine -- suicide bombers struck a parade celebrating her return in October, killing more than 140 people in the southern city of Karachi.

She tried to stage a rally in Rawalpindi last month, but was forbidden by the government and placed under house arrest in Islamabad. She then tried to lead a motorcade from the eastern city of Lahore to Islamabad, but was again placed under house arrest.

The Government finally agreed to the rally after lifting a state of emergency introduced by Mr Musharraf on November 3 to crush opposition to his plans to be re-elected president.

Target

Rawalpindi should be the safest place in Pakistan -- it is the headquarters of the army and home to tens of thousands of members of the armed forces and security services. But their presence also make it a common target for Islamist militants who have carried out a series of suicide bomb attacks there over the last few years.

Earlier yesterday, four people had been killed when gunmen opened fire on a rival rally in Rawalpindi by supporters of Nawaz Sharif, another former prime minister who returned from exile last month.

Security was what passes for tight in Pakistan, with hundreds of riot police manning security checkpoints on the road from Islamabad to Rawalpindi -- partly to stop opposition supporters entering the capital.

Police forced people to pass through metal detectors and undergo body searches before entering the rally site -- a large park decorated with the party's red, black and green flags and huge portraits of Ms Bhutto.

But as so often at political rallies in Pakistan, security was overwhelmed once Ms Bhutto arrived.

She was immediately mobbed by supporters and left with only her personal bodyguards as protection.

The assassin spotted his chance just as she was leaving in her Land Cruiser, standing up through the sunroof to wave at her supporters with characteristic disregard for her own safety. Muhammed Salman, a senior PPP member, said he was standing a few dozen yards from her vehicle when he heard the blast.

"After delivering the speech, she came down the stairs and got in her Land Cruiser. Then we heard three fires [shots] and after that bomb blast went," he said. "When I turned around there were lots of people lying dead in the roads."

Muhammad Shahid, a police officer on duty at the site, said: "The man first fired at Bhutto's vehicle. She ducked and then he blew himself up."

In the confusion, party officials originally said Ms Bhutto had escaped unhurt. But within minutes, they announced she had been wounded and was in surgery, and half an hour later, Rehman Malik, a party official, broke the news of her death.

Martyred

"She has been martyred," he said, prompting wails and sobs from waiting reporters and supporters outside the hospital.

Officials said later about 20 others had been killed. Mr Musharraf placed police and paramilitary forces on "red alert" across the country of 165 million people. "This is the work of those terrorists with whom we are engaged in war," he said, in a televised address last night, announcing three days of mourning. "I want to appeal to the nation to remain peaceful and exercise restraint."

Rioting broke out across the country, killing at least four more people.Thousands of people poured onto the streets of Karachi, Ms Bhutto's main support base, setting fire to several buildings.

Mr Sharif, who went to the hospital, said he would boycott the elections and called on Mr Musharraf to resign immediately.

"I demand that Musharraf quit power, without delay of a single day, to save Pakistan," he told reporters.

Later, Ms Bhutto's supporters mobbed the hospital as her coffin was driven away to a nearby airbase to be flown to her hometown of Larkana, in the southern province of Sindh.

She is expected to be buried there in the next few days in the white marble mausoleum she built for her father and her two dead brothers.(© The Times, London)

- Jeremy Page