The assassination of Pakistani opposition leader Benazir Bhutto has sparked violent riots in the country and raised doubts about whether next month's parliamentary elections will remain on track.

Bhutto was killed in a suicide attack on her SUV as she left a rally in Rawalpindi on Thursday.

Despite an appeal for calm by President Pervez Musharraf, Bhutto supporters continued torching buildings and cars in several cities throughout Pakistan Friday.

At least 23 people have reportedly been killed in riots following the assassination.

In Karachi, mobs looted three banks and set them on fire. Some also became involved in a shootout with police that left three officers injured.

Paramilitary rangers' spokesman Maj. Asad Ali said his men have been given the authority to use live fire on rioters damaging property.

"We have orders to shoot at sight,'' he said.

In the central city of Multan, about 7,000 people raided seven banks and a gas station. The mobs also threw stones at police, who responded with tear gas.

In Islamabad, about 100 protesters burned tires in a commercial area. However, Islamabad was fairly quiet overall, CTV's Paul Workman reported.

Across Sindh province, where Bhutto is from, protesters torched 10 railway stations and several trains, said a senior railway official. One section of tracks leading to the Indian border was also uprooted.

In the northwestern city of Peshawar, about 4,000 Bhutto supporters rallied in support of their party. Several hundred of them later destroyed the office of the main pro-Musharraf party.

Furniture was lit ablaze but nobody was hurt as the office was empty.

Many other cities in Pakistan were virtually deserted Friday as business closed to mark the beginning of three days of national mourning for Bhutto.

Upcoming elections

Bhutto's death has also thrown the country's elections, scheduled for Jan. 8, into question.

Terrorism analyst Eric Margolis told CTV's Canada AM on Friday that the elections had already been viewed with skepticism.

"The elections definitely would be a farce," said Margolis. "They were going to be rigged in any event as have all elections in Pakistan for the last eight years under Musharraf."

Margolis said the original U.S.-promoted plan was to have the elections rigged again so that Bhutto would emerge as prime minister -- with the intention that the real power would remain with Musharraf.

Rasul Baksh Rais, a political scientist at Lahore's University of Management Sciences, told The Associated Press that the assassination is a major setback for democracy.

"It shows extremists are powerful enough to disrupt the democratic process," said Rais. "Musharraf's major concern now will be to maintain law and order and make sure this does not turn into a major movement against him."

On Friday, Prime Minister Mohammedmian Soomro said the government had no plans to delay the elections.

"Right now the elections stand where they were," he told a news conference. "We will consult all the political parties to take any decision about it."

Pakistani opposition leader and former prime minister Nawaz Sharif said on Thursday his party would boycott the election.

If Bhutto's now leaderless Pakistan Peoples Party follows suit, the move would take away any remaining legitimacy surrounding the elections, political analyst Talat Masood told AP.

With files from The Associated Press