Benazir Bhutto's party challenged official versions of the opposition leader's assassination and accused the government today of trying to cover up failures just days before planned elections.
Fresh violence brought the death toll since Bhutto's assassination in a gun and bomb attack on Thursday to 40, stoking fears a January 8th election meant to restore civilian rule to the nuclear-armed U.S. ally could be put off.
Al Qaeda linked militants denied being behind the killing of the 54-year-old former prime minister.
Pakistan's government had said yesterday it had proof of al Qaeda involvement. However, Bhutto's party dismissed this official account, saying there was no solid evidence and President Pervez Musharraf's embattled administration sought to cover up its failure to protect her.
A close Bhutto aide who prepared her body for burial also dismissed as "ludicrous" a government theory that she died after hitting her head on a sunroof during the suicide attack. Sherry Rehman, a spokeswoman for Bhutto's Pakistan People's Party, said Bhutto was shot in the head.
Pakistanis remained on edge today, after protesters torched shops, lorries, welfare centres and ambulances overnight.
In Karachi, masked gunmen shot dead a 27-year-old man wearing a tunic made from the flag of Bhutto's Pakistan People's Party (PPP). He had just shouted "Bhutto is great" while returning from the mausoleum where Bhutto was buried on Friday, police said.
Security forces shot dead two others among 400 PPP activists trying to break into an oilfield facility near Hyderabad, police said.
Late yesterday, Interior Ministry spokesman Javed Iqbal Cheema told a news conference: "We have intelligence intercepts indicating that al Qaeda leader Baitullah Mehsud is behind (Bhutto's) assassination."
However, a spokesman for Mehsud denied the claim. "I strongly deny it. Tribal people have their own customs. We don't strike women," Maulvi Omar said by telephone from an undisclosed location. A PPP spokesman said the government must show hard evidence. "The government is nervous," he said. "They are trying to cover up their failure" to provide adequate security.
So far the government has not announced any decision to call off or postpone the vote, but the Election Commission says it is planning an emergency meeting on Monday.
The opposition party led by former prime minister Nawaz Sharif has said it would boycott the January election if it goes ahead, and a spokesman said today Sharif was trying to convince Bhutto's PPP to do likewise.
President Musharraf imposed a state of emergency in November in what was seen as an attempt to stop the judiciary from vetoing his re-election as president. He lifted emergency rule this month.
Bhutto, who became the Muslim world's first democratically elected woman prime minister in 1988, was buried alongside her father, former Prime Minister Zulfikar Ali Bhutto. He was hanged in 1979 after being deposed by a military coup.