Pakistan's government blamed al Qaeda on Friday for the assassination of opposition leader Benazir Bhutto, and released a conflicting report that claims she died from a skull fracture, not gunshot wounds.

At a press conference Friday, Interior Ministry spokesman Javed Iqbal Cheema said the Pakistani government recorded an "intelligence intercept" in which an al Qaeda leader "congratulated his people" for killing Bhutto.

Cheema identified the "al Qaeda leader" as Baitullah Mehsud.

Mehsud is a commander of pro-Taliban forces in the lawless Pakistani tribal region of South Waziristan -- where al Qaeda forces are also active.

Cheema also said Bhutto died when she was thrown by the force of an explosion and knocked her head into the sunroof of her SUV, moments after she spoke at a political rally.

"One of the levers of the sunroof hit her on the right side, which caused a fracture, and that is what caused her death," Cheema told reporters.

But on Thursday, just hours after the attack, a doctor had said Bhutto was fatally shot twice by a gunman who then detonated an explosive device as Bhutto's vehicle sped away from the scene. Twenty-seven others died in the blast.

Further confusing the issue, the surgeon who treated Bhutto at Rawalpindi General Hospital said she died from a shrapnel wound to the head.

Dr. Mussadiq Khan said Bhutto had shrapnel in the right side of her skull. Khan also said Bhutto had no heart beat or pulse when she arrived at the hospital.

Bhutto's medical report did show no bullet was found in her body, said Cheema.

Masses of mourners

Meanwhile, hundreds of thousands of mourners gathered outside Bhutto's family's mausoleum to pay their final respects.

The funeral procession began Friday afternoon at Bhutto's ancestral residence in the southern town of Naudero.

From there, her plain wood coffin -- wrapped in the red, green and black flag of her Pakistan Peoples Party -- was transported to the mausoleum in Garhi Khuda Baksh.

"This country is in deep shock as a result of what happened," CTV's Paul Workman reported from Islamabad.

"Even those people who did not support Benazir Bhutto really can't accept and can't understand what happened."

Bhutto, 54, was buried next to her father, former prime minister Zulfikar Ali Bhutto, who was removed from power by the military in 1977 and executed.

Rioting kills dozens

In several cities across Pakistan Friday, supporters of Bhutto continued to riot, setting fire to cars and stores as they blamed President Pervez Musharaf for Bhutto's death.

Many believe Musharaf did little to prevent the attack by refusing to boost security for Bhutto, despite constant death threats against her.

In Karachi, people looted banks and fired guns at the police, injuring at least three officers.

Thousands broke into banks in Multan and threw rocks at police, while in the capital of Islamabad, another 100 people set fire to tires.

The military has sent soldiers into the cities to quell the violence and paramilitary rangers in southern Pakistan have the authority to shoot anyone who damages property.

With files from The Associated Press