The suicide attack that killed opposition leader and former Prime Minister Benazir Bhutto has sparked riots in several cities and thrown Pakistan's crucial January elections into doubt. VOA's Barry Newhouse reports on the developments from Washington with reporting from Ayaz Gul in Islamabad.

In what would be her final speech before thousands of supporters in the garrison city Rawalpindi, Benazir Bhutto ended her address with an emotional declaration about the commitment of her Pakistan People's Party.

She said "the honor of Pakistan is our honor and for this honor we all are ready to sacrifice our lives."

A short while later Ms. Bhutto boarded her armored car, thronged by supporters. As she waved to the crowds with her torso extending out of the sunroof, witnesses said a man wearing a suicide vest walked up to the car, shot the 54-year-old opposition leader in the neck, and then detonated a blast that killed at least 20 people.

Ms. Bhutto was rushed to a nearby hospital, where doctors declared her dead Thursday evening.

President Pervez Musharraf later appeared on national television and declared a three-day period of national mourning.

He blamed her assassination on what he called extremists and terrorists who have been threatening Pakistan's integrity. The president vowed to eliminate terrorist forces from Pakistan.

While Ms. Bhutto had frequently expressed concerns about Islamic militants trying to assassinate her, she also said old political foes, including some government officials, could try to kill her.

As news of her death spread, Ms. Bhutto's supporters went on a rampage in several cities across Pakistan, burning vehicles, attacking shops and chanting slogans against President Musharraf.

Several casualties were reported in the riots.

While security forces tried to contain the violence and asked people to stay indoors, Ms. Bhutto's supporters began transporting her body to the family grave in Larkana in southern Sindh province.

Former Prime Minister Nawaz Sharif, one of the country's most popular leaders and an opponent of both President Musharraf and Ms. Bhutto, said his party would boycott the January polls.

The former prime minister also called on President Musharraf to step down.

Ms. Bhutto's Pakistan People's Party and Nawaz Sharif's Pakistan Muslim League Party are the country's two strongest opposition parties and their participation has been considered crucial to ensuring credible elections.