ISLAMABAD, Pakistan -- Pakistan's government said Friday that al-Qaida was behind the assassination of Benazir Bhutto and that she did not die from gunshots or a suicide bomber's shrapnel as first believed.
President Pervez Musharraf's government said Bhutto was killed when her skull was shattered by the force of the bomb blast that slammed her against a lever in her car's sunroof.
Hundreds of thousands, meanwhile, mobbed Bhutto's funeral as the army tried to quell rioting elsewhere that left a total of 27 dead. The popular opposition leader was buried beside her father in a marble mausoleum in the Bhutto ancestral village in southern Sindh province.
The new government's explanations were part of a rapidly evolving political crisis triggered by the death of Bhutto, Musharraf's most powerful foe in the elections. The rioting by Bhutto's furious supporters raised concerns that the nuclear-armed nation, plagued by chaos and the growing threat from Islamic militants even before the killing, was in danger of spinning out of control.
Pentagon officials said they have seen nothing to give them any worries about the security of Pakistan's nuclear arsenal.
To prevent the violence from spreading, the Pakistani government ordered an almost complete shutdown of services. Officials suspended much train service and most domestic flights. Gas stations across the country were closed, making it virtually impossible to make long journeys by car. Roads were closed around city centers, and TV and Internet services were shut down or operated only sporadically in most cities.
Pakistan said it would hunt down those responsible for Bhutto's death in the lawless tribal areas along the Afghan border where Osama bin Laden and other al-Qaida leaders are thought to be hiding.
The government released a transcript of a purported conversation between militant leader Baitullah Mehsud and another militant.
"It was a spectacular job. They were very brave boys who killed her," Mehsud said, according to the transcript. The government did not release an audiotape.
Interior Ministry spokesman Javed Iqbal Cheema described Mehsud as an al-Qaida leader who was behind most other recent terror attacks in Pakistan, including a Karachi bomb blast in October against Bhutto that killed more than 140 people.
Mehsud is thought to be the commander of pro-Taliban forces in the tribal region of South Waziristan, where al-Qaida fighters are active.
In the transcript, Mehsud gives his location as Makin, a town in South Waziristan.
This fall, he was quoted in a Pakistani newspaper as saying he would welcome Bhutto's return from exile with suicide bombers.
Mehsud later denied that in statements to local TV and newspaper reporters.
Cheema announced the formation of two inquiries into Bhutto's death, one to be carried out by a high court judge and another by security forces.
Bhutto was assassinated Thursday evening after a rally in the garrison city of Rawalpindi near Islamabad. Twenty other people died in the attack.
On Thursday, authorities had said Bhutto died from bullet wounds fired by a young man who then blew himself up. A surgeon who treated her, however, said Friday she died from the impact of shrapnel on her skull.
But later Friday, Cheema said those two accounts were mistaken.
He said all three shots missed her as she greeted supporters through the sunroof of her vehicle, which was bulletproof and bombproof.
He also denied shrapnel caused her death, saying Bhutto was killed when she tried to duck back into the vehicle, and the shock waves from the blast knocked her head into a lever attached to the sunroof, fracturing her skull. The government released a photo showing blood on the lever.
Denying charges that the government failed to give her adequate security protection, Cheema said it was Bhutto who made herself vulnerable and pointed out that the other passengers inside Bhutto's bombproof vehicle were fine.
"I wish she had not come out of the rooftop of her vehicle," he said.
Rioters in the southern city of Karachi torched 500 vehicles, 13 banks, seven gas stations and two police stations, Police Chief Azhar Farooqi said. The violence killed 13 people, including five workers in a garment factory that was set ablaze, police said. A shootout between rioters and police wounded three officers, police said.
Six people died from suffocation in Mirpurkhas, about 200 miles northeast of Karachi, when a bank building was set on fire, said Ghulam Mohammed Mohtaram, the top civilian security official in Sindh province.
About 7,000 people in the central city of Multan ransacked seven banks and a gas station and threw stones at police, who responded with tear gas. Media reports said 200 banks were attacked nationwide.
Vandals also burned 10 railway stations and several trains across Sindh province, forcing the suspension of all train service between Karachi and the eastern Punjab province, said Mir Mohammed Khaskheli, a senior railroad official.
Desperate to quell the violence, the government sent troops into the streets of Hyderabad, Karachi and other areas in Sindh.
