Nationwide unrest kept daily life in Pakistan literally paralyzed for the second day Saturday following the assassination of opposition leader Benazir Bhutto, as her supporters rejected government claims that Taliban militants killed her.

Business activities were suspended and roads mostly empty in cities and towns due to a three-day mourning period ordered by President Pervez Musharraf, but also because of the riots that have claimed more than 30 lives so far and destroyed hundreds of buildings, vehicles, banks and homes.

Thousands of military and paramilitary troops, operating under shoot-on-sight orders, continued patrolling several cities in the southern province of Sindh, a political stronghold of Bhutto, whose enraged supporters have set on fire hundreds of vehicles, dozens of railway stations and government buildings.

As the sense of uncertainty and insecurity deepened across the country, the controversy over official explanations of Bhutto's death was growing due to conflicting statements from government officials.

Initially, health officials said she died from bullets fired by the assassin, who then blew himself up as Bhutto was waving to the crowd from the sunroof of her bullet-proof vehicle after a campaign rally in Rawalpindi on Thursday afternoon.

But Interior Ministry spokesman Javed Iqbal Cheema claimed late Friday that the medical report showed that Benazir died due to a fatal fracture in her skull after hitting an iron lock on the sunroof of her vehicle.

"However, she was also fired at but not a single bullet hit her," he said.

The spokesman also said authorities had intercepted a telephone conversation proving that a pro-Taliban militant commander, Baitullah Mehsud, who is also believed to have close ties with al-Qaeda, was behind the attack on Bhutto.

However, Bhutto's Pakistan People's Party (PPP) rejected the explanation as a cover up.

"It was a targeted killing by sharp shooter. We reject the explanation of the Interior ministry and we demand the same sort of international inquiry into the murder of Benazir Bhutto as it was conducted in the case of assassinated prime minister of Lebanon Rafiq Hariri," said Farhatullah Babar, a party spokesman.

Babar noted that the government also blamed Mehsud for a suicide attack on Bhutto's home coming rally in southern port city of Karachi in October that narrowly missed her but killed 140 people.

"We do not know it is a genuine transcript or a one crafted in a dark room by the intelligence agencies," he said of the electronic intercept of Mehud.

Analysts said the government's explanations will make it more difficult to pacify angry PPP supporters, who have taken to the streets for the last three days, triggering the worst disturbances in Pakistan in more than three decades.

At least 20 people were injured on Saturday morning by gunfire in Karachi, where at least 17 people have killed and 59 injured in three days of rioting. City Police Chief Azhar Ali Farooqi said rioters had set ablaze more than 500 vehicles, 18 bank buildings, 10 factories, eight petrol stations and two restaurants.

The chaos has diminished the prospects of January 8 parliamentary elections being held as scheduled. Former prime minister Nawaz Sharif has already announced that his party will boycott the vote, while PPP will be observing a 40-day mourning period for Bhutto.

The Pakistani government said Friday that the election was still scheduled to be held but did not rule out a delay.

"We will take a decision on the issue only after consulting the all political parties," caretaker Prime Minister Mohammedmian Soomro told reporters after a cabinet meeting in Islamabad.

The United States initially urged Pakistan to go ahead with the election plan, saying a delay would be a victory for "extremists," but has since indicated it would support a brief delay.

US State Department spokesman Tom Casey said Friday that his government "wasn't trying to convey that there's something magic about January 8."

"If political parties and actors in the country come to some different conclusion, then certainly we'll take a look at it then," he said.