The two sides cannot agree whether she was shot or suffered fatal blast injuries. The dispute could influence the future direction of two inquiries announced yesterday by the Pakistani government.
Any evidence that a lone suicide bomber carried out the attack would support the government's assertion that al-Qaeda was responsible; proof that shots were fired would fuel the suspicion of many within Bhutto's Pakistan People's Party (PPP) that elements within the Pakistani state were to blame.
Meanwhile, with outbreaks of disorder continuing in several cities, and large parts of the country paralysed because transport workers, storekeepers and bank staff are too terrified to leave their homes, there was no sign last night that investigators were any closer to bringing the killers to justice.
Witnesses spoke of hearing two, or possibly three, gunshots before the bomb was detonated as Bhutto left a political rally in the northern city of Rawalpindi last Thursday. Party officials sitting in their leader's car say she had clearly been shot twice, in the neck and shoulder. However, the interior ministry now maintains that she died after her head was dashed against the inside of the vehicle's sunroof, probably by the force of the explosion.
Any suggestion that she died because her head was exposed to the blast would allow the authorities to insist that she had exposed herself to danger, and absolve themselves of charges that they failed to protect the leader of the opposition.
It would also support the authorities' allegation of an al-Qaeda connection, an accusation they have bolstered by claiming to possess evidence that the attack was ordered by Baitullah Mahsud, a militant commander from the border area of South Waziristan, a remote mountainous region bordering Afghanistan. The government yesterday stuck to its version of events, and said Bhutto's party was welcome to exhume her corpse to check.
Branding Mahsud as a leading al-Qaeda terrorist, the Pakistan interior ministry claims that it has recorded a telephone conversation between him and another man in which they congratulated themselves on the politician's death.
While Mahsud, 34, does enjoy strong links with the Taliban, he has already denied any involvement in October's attempted murder of Bhutto in a double suicide bomb attack, and yesterday his spokesman denied he was involved in Thursday's assassination. 'It is against tribal tradition and custom to attack a woman,' the spokesman said.
The PPP dismissed the claim that Bhutto suffered no gunshot wounds as 'dangerous nonsense' and demanded the assassination be investigated by international experts. A definitive account of the cause of death may never be established, however, because Bhutto's husband, Asif Zardari, did not give permission for a post-mortem examination before she was buried on Friday.
Britain said yesterday it had no reason to doubt the government's account of the murder. David Miliband, the Foreign Secretary, said: 'We have followed carefully the reports from the Pakistani government and we have no evidence to contradict the reports that are coming out of Pakistan.' He offered Britain's support for the inquiries into Bhutto's death. One will be led by a high court judge and the other will be carried out by the security forces.
It remained unclear yesterday whether elections will go ahead on 8 January as planned. In Washington, the State Department has urged that the polls go ahead as scheduled, or shortly after that date. But the Pakistani government has decided to consult the leaders of all the country's political parties before making a decision, and Pakistan's leader, Pervez Musharraf, says he is waiting to hear today whether the PPP will take part in those discussions.
The disorder that has swept the country since Thursday was particularly marked in the southern province of Sindh, where masked gunmen murdered a PPP supporter and two other activists were shot dead by police while attempting to break into an industrial facility. Those deaths brought the toll to at least 38 since Thursday's assassination. In addition, according to the interior ministry, rioters have burnt down 174 banks, and destroyed 18 rail stations. About 100 prisoners have been sprung from jails.
In Karachi, the port city of 14 million people that is the capital of Sindh, three people were shot dead and a further 17 wounded, while large areas of the city were reported to be virtually deserted, with police and paramilitary forces patrolling the streets. In Rawalpindi, police fired tear gas to disperse stone-throwing protesters who marched through the streets after gathering at a memorial service close to the spot where Bhutto's car was bombed.
In Islamabad, police sealed off the administrative district for several hours, while a march by students attracted thousands more protesters.
Bhutto, 54, a mother of three who became the Muslim world's first democratically elected woman prime minister in 1988, was buried alongside her father, former prime minister Zulfikar Ali Bhutto. Her will is to be read today, and there is speculation that she may have used the testament to name her preferred successor as leader of the PPP.
Guardian Unlimited © Guardian News and Media Limited 2007