Bhutto said there were two attackers in the deadly bombing, and that her security guards found a third man armed with a pistol and another with a suicide vest. Ahead of her arrival, she said, she was warned suicide squads were dispatched to kill her.
CBS News' Farhan Bokhari reported that Bhutto's return to Pakistan had been preceded by intelligence reports suggesting that members of Al Qaeda were planning to target her.
According to CBS News correspondent Sheila MacVicar, even before her return, Bhutto was so convinced there would be an assassination attempt that she sent the names of three suspected conspirators to Pakistan's president and a senior American journalist, Arnaud de Borchegrave.
The message read, "I have been informed that Baitur Massoud, an Afghan; and Hamza bin Laden, an Arab; and a Red Mosque militant have been sent to kill me."
Upon her arrival on Thursday, she set aside the security plan to be visible only from behind a bullet proof glass and instead chose to stand on an elevated platform, raising objections from Karachi police officials who said Bhutto had compromised her security.
The first blast came from a suicide bomber who got through lines of police protection. A second, bigger bomb transformed the streets into a burning hell of burning bodies, some with terrible injuries, others simply dead from the explosion, MacVicar told The Early Show.
Bhutto survived unscathed, but the back-to-back explosions that went off near a bulletproof truck in which she was riding turned her jubilant homecoming parade through the city streets into a scene of blood and carnage, ripping victims apart and hurling a fireball into the sky. The attack shattered the windows of her truck. She appeared dazed afterward and was escorted to her Karachi home.
"There was one suicide squad from the Taliban elements, one suicide squad from al Qaeda, one suicide squad from Pakistani Taliban and a fourth - a group - I believe from Karachi," she said.
Baitullah Mehsud, a top militant leader on the unstable Afghan border, threatened this month to meet Bhutto's return to Pakistan with suicide attacks, according to local media reports. An associate of Mehsud, however, denied Taliban involvement.
Bhutto said her guards prevented more carnage.
"They stood their ground, and they stood all around the truck, and they refused to let the suicide bomber - the second suicide bomber - get near the truck," she said.
"We believe democracy alone can save Pakistan from disintegration and a militant takeover," she told a news conference. "We are prepared to risk our lives and we are prepared to risk our liberty, but we are not prepared to surrender our great nation to the militants."
She did not blame the government, but said it was suspicious that streetlights failed after sunset Thursday when her convoy was inching its way through the streets of Karachi. She said attempts to reach the national security advisor to have the lights restored were unsuccessful - phone lines were also apparently down.
"I'm not accusing the government but certain individuals who abuse their positions and powers," she said. "We were scanning the crowd with the floodlights, but it was difficult to scan the crowds because there was so much darkness."
Pakistan did everything it could to protect Benazir Bhutto on her homecoming, a top government official insisted on Saturday, dismissing accusations that officials may have been complicit in the attack.
"I think we should stop playing blame games. The government provided the best possible security to her," Deputy Information Minister Sen. Tariq Azim told The Associated Press. "The trauma of the attack has made them say things which probably in coolness of things they will not repeat."
"Peoples names have been mentioned and names have been hinted at without giving any reason or without giving any proof of their involvement, and that is unfair," he said.
Bhutto said the next attack against her would target her homes in Karachi and her hometown of Larkana, using attackers posing as supporters of a rival political faction.
She blamed the attack on militants trying to quash democratic reforms.
The attack - one of the deadliest in Pakistan's history - bore the hallmarks of militants linked to pro-Taliban warlord Baitullah Mehsud and al Qaeda, according to Ghulam Muhammad Mohtarem, the top security official in Sindh province, where Karachi is located. He suggested that Bhutto's camp had gotten carried away celebrating her return after eight years in exile, and had not taken the need for security seriously.
"We were already fearing a strike from Mehsud and his local affiliates and this was conveyed to the (Bhutto's Pakistan's) People's Party but they got carried away by political exigencies instead of taking our concern seriously," Mohtarem said.
President Gen. Pervez Musharraf, the nation's leader, phoned Bhutto Friday to express his shock and profound grief over the bombing and prayed for the former premier's safety and security, his spokesman said.
"The president and Ms. Bhutto both expressed their unflinching resolve to fight this scourge of extremism and terrorism. They also agreed that there was a need for the entire nation to unite in order to rid the country of this menace of suicide bombings, terrorism and extremism," Qureshi said.
Musharraf resolved to "bring the perpetrators of this heinous crime to justice."