The FBI and Homeland Security reportedly told U.S. law enforcement agencies that al-Qaida has claimed responsibility for the assassination of Pakistani opposition leader Benazir Bhutto.

Link: CNN Coverage

That word came in a bulletin that a law enforcement official summarized for The Associated Press. The official asked to remain anonymous, because he's not authorized to speak publicly about the bulletin.

The bulletin cites Islamist Web sites as the sources of the al-Qaida claim. The sites also say that al-Qaida's No. 2 leader, Ayman al-Zawahri, had planned the assassination. Al-Zawahri decried Bhutto's return in a video message this month and called for attacks on all the candidates in Pakistan's parliamentary elections.

Bhutto had pledged to redouble Pakistan's fight against Islamic militants. She had received threats from virtually all militant groups that make Pakistan their home. That includes al-Qaida, as well as Taliban-style radicals and tribal insurgents along the Afghan border.

Riots Break Out Following Death

At least nine deaths were reported across Pakistan Thursday in rioting that broke out following Bhutto's assassination.

The 54-year-old former Pakistani prime minister was killed by an attacker who shot her after a campaign rally and then blew himself up. She was rushed to an area hospital for emergency surgery, but died about an hour later.

At least 20 others also died in the attack in Rawalpindi, Pakistan.

The government announced three days of mourning for Bhutto, including the closing of schools, commercial centers and banks.

Meanwhile, Pakistan rumbled with grief and fury after the assassination. Angry supporters took to the streets in the northwestern city of Peshawar as well other areas, attacking police and burning vehicles and tires.

One man was killed in a shootout between police and protesters in a town north of Karachi. Two people were killed in the southern Sindh province and two others in Lahore.

At the hospital where Bhutto died, some backers smashed glass and chanted slogans against Prime Minister Pervez Musharraf, accusing him of complicity in her killing.

In televised speeches, Musharraf condemned the assassination, blamed terrorists for her death, and said he would redouble his efforts to fight them.

Musharraf also appealed for calm in the streets, but Nawaz Sharif, the leader of a rival opposition party, told mourners at the hospital that he would help them "take the revenge for her death."

Bhutto's Body Leaves Hospital

Bhutto's body was carried out of a hospital in a plain wooden coffin by a crowd of her supporters on Thursday.

Bhutto's remains were expected to be transferred to an air base and taken to her hometown of Larkana.

A doctor on the team that treated Bhutto said she had a bullet in the back of the neck that damaged her spinal cord before exiting from the side of her head. Another bullet pierced the back of her shoulder and came out through her chest.

A man who said he witnessed the assassination said he was standing about 10 yards away from Bhutto's white, bulletproof SUV.

The witness, a leader of Bhutto's party, said Bhutto was inside the SUV and was leaving a campaign rally when some young supporters began chanting slogans. He said he saw a smiling Bhutto emerge through the vehicle's sunroof.

Then, said the witness, he saw "a thin, young man" jumping toward Bhutto's vehicle from the back and opening fire. Moments later, he saw Bhutto's vehicle speed away.

Bhutto's death came ahead of parliamentary elections next month in which her party was expected to do well.

Her death leaves her party without a leader and the election schedule in doubt.

An official at Pakistan's Interior Ministry said shortly after Bhutto's death that Musharraf convened an emergency meeting with his senior staff to discuss whether to postpone the election.

Sharif said his party would boycott the elections.

Bhutto was killed just a few miles from the scene of her father's violent death 28 years earlier. He was executed by hanging in 1979 on charges of conspiracy to murder that supporters say were politically motivated by the then-military regime.

She served twice as Pakistan's prime minister between 1988 and 1996, and she had returned to Pakistan from an eight-year exile on Oct. 18, saying she knew she risked death.

Her homecoming parade in Karachi was also targeted by a suicide attacker, who killed more than 140 people. She narrowly escaped injury.

U.N. Seeks 'Restraint'

The U.N. Security Council unanimously condemned the assassination and urged all nations to help bring those responsible to justice.

After a two-hour emergency session, it described Bhutto's killing as a threat to international peace and security and said it "calls on all Pakistanis to exercise restraint and maintain stability in the country."

U.S. ambassador to the U.N., Zalmay Khalilzad, called Bhutto a close personal friend and "courageous figure" whose death now poses a threat to Pakistan's democratic process.

U.N. Secretary-General Ban Ki-moon said he was "shocked and outraged" by Bhutto's assassination.

U.N. officials said they did not discuss whether Pakistan's government could have done more to protect Bhutto.

The U.S. State Department issued a statement condemning the attack Thursday.

"Certainly, we condemn the attack on this rally," said deputy State Department spokesman Tom Casey. "It demonstrates that there are still those in Pakistan who want to subvert reconciliation and efforts to advance democracy."

For months, the United States has been encouraging Musharraf to reach some kind of political accommodation with his opponents, particularly Bhutto.

President George W. Bush, speaking from his Crawford, Texas, ranch, sent his condolences to Bhutto's family and to the families of those who were killed.

"The United States strongly condemns this cowardly act by murderous extremists," Bush said. "Those who committed this crime must be brought to justice."

Analysts Weigh In On Impact

Analysts are weighing in on Bhutto's assassination and how it may impact Pakistan's relationship with the U.S.

Daniel Markey, a senior fellow at the Council on Foreign Relations, said the attack may reinforce beliefs that Pakistan is dangerous, messy and "potentially very unstable and fragile." But, he said the Bush administration still considers Musharraf more helpful than harmful.

Other experts said the U.S. doesn't have much leverage. Wendy Sherman, who served under former Secretary of State Madeleine Albright, said Pakistan's people and their government will be making their own decisions.

Christine Fair, an expert on South Asia, warned that the assassination may embolden militants to target other high-profile leaders. She said the U.S. doesn't have a contingency plan because Musharraf is still a critical ally and Bhutto was supposed to legitimize upcoming elections.