Pakistan's government blamed al-Qaeda and the Taliban on Friday for the assassination of opposition leader Benazir Bhutto, claiming intelligence agents intercepted a message of congratulation from a militant leader.

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Afghan President Hamid Karzai walks with former Pakistani prime minister Benazir Bhutto after a meeting in Islamabad on Thursday, just hours before Bhutto's assassination. ((Farooq Naeem/AFP/Getty Images))

Interior Ministry spokesman Brig.-Gen. Javed Iqbal Cheema said that on Friday the government recorded an "intelligence intercept" from an "al-Qaeda leader," Baitullah Mehsud.

In the message, Mehsud "congratulated his people for carrying out this cowardly act," Cheema said.

The Pakistani government released a transcriptof the intercepted conversation between Mehsudand another man identified as Maulvi Sahib.

"It was a spectacular job. They were very brave boys who killed her,"Mehsud is quoted as saying.

Earlier, Interior Minister Hamid Nawaz said the government had evidence that al-Qaeda and the Taliban were behind the suicide attack.

Cheemasaid Mehsud was also behind the dual bomb blasts on Oct. 19 in Karachi that killed more than 140 people celebrating Bhutto's return to her hometown. Bhuttoescaped that attack uninjured.

Bhutto was killed along with 20 others by a suicide attacker Thursday shortly after she spoke ata campaign rally in the northern city of Rawalpindi.

The opposition leader's assassination has plunged Pakistan into turmoil as her supporters burned cars and businesses in several cities to protest her killing. At least 23 people have been killed in riots since her death was announced.

Dispute over cause of death

Conflicting reports again emerged Friday over the cause of Bhutto's death. Initial reports Thursday said she died from gunshot wounds to the neck and chest, but a surgeon whotreated Bhutto said she died from a shrapnel wound to the head.

Bhutto had no heartbeat when she arrived at the hospital and doctors failed in their efforts to resuscitate her,the Associated Press quotedDr. Mussadiq Khan, a surgeon who treated her, as saying Friday.

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Interior Ministry spokesman Brig.-Gen. Javed Iqbal Cheema says the government recorded an 'intelligence intercept' on Friday from an al-Qaeda leader congratulating those who carried out the assassination. ((CBC))

But the Interior Ministry's Cheema said all three shots missed her as she greeted supporters through the sunroof of her vehicle, which was bulletproof and bombproof. He also denied that shrapnel caused her death.

Instead, Cheema said, Bhutto was killedafter 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.

"We pray and wish that she had not come out of that sunroof to wave at the people," he said.

John Moore, a Getty Images photographer who was in the crowdoutside Bhutto's vehicle during herlast moments, told CBC News he was shocked to see the former prime minister standing through the vehicle opening. He said he worried for everyone's safety, as the rally was publicized a week in advance, giving potential attackers time to plan.

"I couldn't believe my eyes, just because of what happened in Karachi with the assassination attempt just a couple ofmonths ago," he said in a phone interview. "But she wanted to get close to the people. She loved being in close contact, they loved her, and she thought it was worththe risk."

Moore, however, could not confirm whether it was the gunshots or the blast that killed Bhutto.

"I heard the shots, and she went down and the explosion happened. Did I see the impact of the bullets? I did not. It all happened at almost the same time. So the version of events is still very unclear at this point."

Cheema defended the security detail the government provided to Bhutto as the largest ever givento a former prime minister.

"We had provided her four mobile units whenever she was on the move," he said, adding that the mobile units contained six agents each.

Bhutto's security adviser criticized the governmentfor failing to provide adequate measures for her protection, including bomb-jamming devices that fill the surrounding area with radio waves thatinterrupt remote detonation signalstoexplosive devices.

But Cheemainsisted the devices would not have prevented a suicide attacker from detonating his explosives manually.

"The best protection against a terrorist attack is the vehicles," he said.

With files from the Associated Press