ISLAMABAD - Masked gunmen shot dead a supporter of slain Pakistan opposition leader Benazir Bhutto on Saturday, as violence triggered by her assassination entered a third day and al Qaeda-linked militants denied killing her.

Pakistan's government had said on Friday it had proof al Qaeda was behind the suicide attack on the 54-year-old former prime minister, whose death has plunged the nuclear-armed country into crisis and triggered bloody protests.

But a spokesman for the al Qaeda leader the government blamed denied involvement, and Bhutto's party dismissed the official explanation, saying President Pervez Musharraf's embattled administration was trying to cover up its failure to protect her.

Pakistanis remained on edge on Saturday, after protesters torched shops, lorries, welfare centres and ambulances overnight.

"There's a lot of rioting going on in my neighbourhood, Clifton. Everything has been burned up. Shops have been looted," Ali Khan, 36, country manager for Audi Pakistan, told Reuters as he stood outside his Audi garage in Karachi's business district.

In Karachi, a 27-year-old man wearing a tunic made from a Pakistan People's Party (PPP) flag was killed by gunmen. He had just shouted "Bhutto is great" while returning from the mausoleum where Bhutto was buried on Friday, police said.

The killing brought to 33 the death toll from violence since Thursday's gun and bomb attack, stoking fears a January 8 election meant to restore civilian rule to the U.S. ally could be put off.

MILITANT LEADER

Late on Friday, 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 spokesman for Bhutto's Pakistan People's Party said the government must show solid evidence.

"The government is nervous," he said. "They are trying to cover up their failure" to provide adequate security.

Tens of thousands of Bhutto's supporters wept and beat their heads as she was laid to rest on Friday. Troops were called out to quell protests in her home province of Sindh, where she had huge support, particularly among the rural poor.

Bhutto's husband, Asif Ali Zardari, told the BBC her will would be read out to a meeting of the PPP by her son on Sunday.

Asked if he wanted to lead the party, Zardari replied: "It depends on the party and it depends on the will."

Many mourners chanted slogans against Musharraf and the United States, which backs the former general in the hope he can ensure stability in the face of Islamist violence and relies on Pakistan as an ally against al Qaeda and Afghanistan's Taliban.

Musharraf seized power in a military coup in 1999 but left the army last month to become a civilian president.

BLAST

Bhutto returned home from self-imposed exile in October, hoping to become prime minister for a third time.

She died when the force of the blast from a suicide bomber smashed her head into the sun-roof of her car, moments after she had waved to supporters at a rally, the Interior Ministry said.

Washington had encouraged Bhutto, relatively liberal by Pakistan standards and an outspoken opponent of Islamic militancy and violence. Her death wrecked U.S. hopes of a power-sharing agreement between her and Musharraf.

An al Qaeda role, if confirmed, would show how dramatically the group could still thwart U.S. foreign policy, analyst said.

U.S. President George W. Bush has urged Pakistanis to honour Bhutto's memory by going ahead with the election.

So far the government has not announced any decision to call off or postpone the vote, but analysts and some other Pakistanis said the assassination, following a wave of suicide attacks and the worsening of an Islamist insurgency, could make going ahead difficult.

"I don't think holding an election is possible," said Mohammad Rashid, 34, a Karachi resident, who believed the official version of Bhutto's death was a lie.

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 on Saturday Sharif was trying to convince Bhutto's Pakistan People's Party to do likewise.

"(Sharif) has gone into the same mode as when he arrived in Pakistan. He feels elections under Musharraf are just useless, that Musharraf is the problem and his removal is more important than elections," Nadir Chaudhri said by telephone.

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.

Bhutto escaped unhurt from a suicide attack in October that killed about 140 people. The government said al Qaeda was also behind that attack.

She had spoken of al Qaeda plots to kill her. But she also had enemies in other quarters, including among the powerful intelligence services and some allies of Musharraf.