The blast at Lahore High Court, minutes before a planned anti-government rally by lawyers, was a bloody reminder of the security threats facing this key U.S. ally ahead of Feb. 18 parliamentary elections.
Echoing an extremist tactic in Iraq, suicide attacks have become as commonplace in Pakistan as in neighboring Afghanistan, adding to rising pressures on President Pervez Musharraf as he struggles to stay in office eight years after seizing power in military coup.
At least 20 suicide bombers have struck the past three months in attacks that killed 400 people, many of them from the security forces - the most intense period of terror strikes here since Pakistan allied with the U.S. in its war against al Qaeda and other extremist groups in 2001.
Police said the attacker got into the midst of some 70 officers in riot gear and detonated explosives on his body, spewing shrapnel in a blast that sprawled mangled bodies in pools of blood. All but three of the dead were police officers.
A horse lay dead, still harnessed to a cart. An abandoned motorcycle was toppled in the street a few yards away. Police boots, riot shields and helmets littered the ground.
"There was a huge bang," said Munrian Bibi, 60, a school cleaner caught in the blast as she headed home from work. "I saw people falling on ground crying for help. I don't know what saved my life from that hell," she said in a hospital where she was treated for leg wounds.
There was no claim of responsibility. The government has blamed previous attacks on Islamic radicals allied with al Qaeda and the Taliban who are intent on expanding their reach from strongholds in Pakistan's lawless tribal region along the Afghan border.
Musharraf blamed the same militants for the Dec. 27 gun and suicide bomb attack that killed Bhutto, a secular former prime minister who had repeatedly pledged to battle Islamic extremism in this country of 160 million people.
Bhutto's supporters have questioned whether elements within the government may have had a role in the opposition leader's slaying after a campaign rally, and are demanding an independent U.N. investigation.
To allay critics, Musharraf last week invited British police to help investigate the attack. The small team of Scotland Yard investigators was in Lahore on Thursday to examine evidence stored at forensic laboratories, but that was far from the bombing site.
The attack in Lahore, which until Thursday had been spared the worst of Pakistan's rising violence, shattered windows and set off tear gas shells carried by the police, preventing people from getting close to the victims in the moments after the blast, witnesses said.
"A man rammed into our ranks and soon there was a huge explosion," said police officer Syed Imtiaz Hussain, who suffered wounds to his legs and groin. "I saw the bodies of other policemen burning. It was like hell."
The city police's chief investigator, Tasaddaq Hussain, said the mutilated head of the suicide bomber had been recovered and would be reconstructed for identification. The bomber's other body parts were being examined by forensic experts to extract DNA, he said.
"The bomber seems to be a young man who was wearing a track suit. He had a thin beard," Hussain said.
Police experts estimated the bomb contained up to 30 pounds of explosives.
The attack occurred about 15 minutes before lawyers planned to demonstrate in front of Lahore's courthouse as part of a nationwide protest movement against Musharraf for the November ouster of independent-minded Supreme Court judges who could have ended his rule.
Although it did not appear the lawyers were the target, the bombing could stifle further street protests and the willingness of Pakistanis to attend election rallies.
But Shamim Akhtar, secretary of the Lahore Bar Association, said the lawyers' struggle would continue. "Such cowardly acts cannot deter us from our struggle against authoritarian rule," he said.
Information Minister Nisar Memon said the bombing was an attempt to scare people from participating in the democratic process. He vowed the national election would go ahead next month and said those responsible for the attack would be captured.
"We are after them. We will get them. They are on the run," he told Dawn News TV.
"With such bloody violence taking place in Pakistan, there must be questions on security conditions as this country heads towards elections" one western diplomat told CBS News' Farhan Bokhari on condition of anonymity.
Late last month in Lahore, intelligence agents arrested a retired army major with alleged links to al Qaeda and linked him to a Nov. 1 bombing of an air force bus that killed eight people and wounded 40 in the town of Sargodha. It was not clear if that arrest, disclosed this week, was tied in any way to the courthouse bombing Thursday.
Musharraf condemned the latest bombing and reiterated his resolve to fight terrorism, saying he was "not to be deterred by such acts," the state news agency reported.
But Bhutto's husband and political heir, Asif Ali Zardari, said the attack was further proof the president had "miserably failed" to maintain law and order.
The attack came on the eve of the Islamic month of Muharram, which is often marred by bombings and clashes between Pakistan's Sunni Muslim majority and its Shiite minority. Authorities had already boosted security at holy sites across the country.
In the past 20 years, reports Bokhari, hardline Sunni Muslim groups have campaigned to officially have members of the Shiite sect declared heretics.
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