Elsewhere, a suicide bomber blasted a political gathering Saturday in northwestern Pakistan, killing at least 25 people, wounding dozens and stoking fears about security surrounding this month's parliamentary election.
The blast went off inside a hall where about 200 supporters of the Awami National Party - a secular, ethnic Pashtun group - had gathered in the town of Charsadda in the turbulent North West Frontier province, where Islamic extremists operate.
Mohammed Khan, a local police official, said two policemen were among the 20 dead. Four or five children were killed or injured, he said.
Abdul Waheed, 22, who suffered burns from the blast, told The Associated Press from his hospital bed in the nearby city of Peshawar that the bomb went off as an Awami National Party member was reciting verses from Quran, Islam's holy book. He said he did not see the bomber.
"I only heard the blast and cries and then something hit me and I fell down," he said.
TV footage of the aftermath showed the hall, located in the sprawling residence of a party activist, littered with bloodstained clothes, shoes, police caps and wrecked chairs.
Khan said police had found the severed head of the suspected bomber.
Interior Minister Hamid Nawaz said the attacker detonated his explosives "very close to the stage" where party officials were assembled.
Afrasiab Khattak, the party's provincial leader and a prominent human rights champion, was addressing the rally but told Dawn television that he was not hurt.
Nawaz said Islamic militants were threatening all the political parties in the northwest ahead of the Feb. 18 parliamentary elections.
"They are against everyone," he told Dawn News TV.
It was the third suicide attack targeting politicians in the Charsadda area in just eight months.
In April 2007, a suicide bomber attacked a political rally by former interior minister Aftab Khan Sherpao, killing 28 people. Sherpao, who hails from a nearby village and was the top civilian security official in the outgoing government, was slightly injured.
In December, a suicide bomber targeted Sherpao again amid hundreds of holiday worshippers at a mosque inside his home, killing at least 50 people. Sherpao was unhurt.
Days later, opposition leader Benazir Bhutto was killed in a suicide attack in the northern city of Rawalpindi, an attack the government blamed on Taliban militant commander Baitullah Mehsud.
Elsewhere Saturday, a roadside bomb wounded six paramilitary soldiers in southwestern Pakistan, local police official Allah Ditta said.
The attack happened at Naushki, about 90 miles southeast of Quetta, the capital of southwestern Baluchistan province.
Meanwhile in the capital Islamabad, riot police used water cannons and tear gas against hundreds of lawyers protesting the detention of Pakistan's deposed chief justice.
The violence underscored the high tensions in Pakistan as it heads toward eb. 18 elections that are meant to restore democracy after years of military rule. The campaign has been overshadowed by Bhutto's killing in a suicide attack six weeks ago.
Bhutto's Husband Calls For Pakistanis To "Save" Nation
Striving to fill the void left by former Prime Minister Bhutto, her husband Asif Ali Zardari urged followers of her Pakistan People's Party to push for victory in the vote and to realize Bhutto's vision of providing jobs and ending poverty.
"I have the responsibility to save Pakistan," Zardari told the crowd at what was by far the biggest rally in the election campaign so far. "This is our country and we have to save it."
Describing Bhutto as the mother of all Pakistanis, Zardari claimed she had been murdered by an establishment that she wanted to change.
"That is why they were against us," Zardari said. "If they try to stop me, I will destroy them and I hope you people will support me."
The government has rejected allegations that intelligence agents or radicals in the ruling party, allied with President Pervez Musharraf, had plotted to kill her. The government has said the attack was orchestrated by a top Taliban commander with links to al Qaeda.
Police officer Bashir Baluch estimated 100,000 people packed the rally at a stadium in the historic southern town of Thatta. Many thousands more spilled onto the streets outside the full stadium. About 2,000 officers were deployed to provide security.
In Islamabad, hundreds of riot police clashed with about 1,500 black-suited lawyers who marched on the residence of Iftikhar Mohammed Chaudhry, the deposed top judge of the Supreme Court who was fired by Musharraf three months ago and remains under house arrest.
After the lawyers tried to breach a barbed-wire barricade, police drove them back by firing tear gas and shooting water cannons from a fire truck. They also baton-charged the crowd and beat protesters.
Several protesters, including Athar Minallah, a prominent Supreme Court lawyer, were arrested. "I don't know where they are taking me," he told The Associated Press by cell phone from a police van. He said he had been hit on the head by police.
Earlier Saturday, Pakistan's Bar Council announced a nationwide lawyers' boycott of courts until Feb. 18 elections - part of a campaign to pressure the government to restore the chief justice and 60 other top judges who were fired by Musharraf on Nov. 3 ahead of a key Supreme Court ruling on the legality of the U.S.-backed leader's re-election as president.
In the upcoming parliamentary elections, Bhutto's party is widely expected to benefit from the unpopularity of Musharraf and sympathy over the former prime minister's assassination.
It remains to be seen, however, if Zardari can unite her party and dispel public doubts over his track record. He was labeled "Mr. 10 Percent" over his alleged pilfering of state funds and demands for kickbacks during Bhutto's two administrations in the late 1980s and 1990s.
Pir Bakhsh, a 24-year old laborer, said that Zardari's reputation was not good but that love for Bhutto "compels us to attend this rally."
A vast portrait of Bhutto, alongside a picture of her 19-year old son Bilawal, dominated the backdrop of the stage where Zardari spoke. Bilawal, currently studying at Oxford University, was appointed party chairman after her death, but Zardari is the de facto leader.
The rally came a day after Scotland Yard released its findings that a bomb, not a bullet, killed Bhutto after an election rally in the northern city of Rawalpindi on Dec. 27. That supported the conclusion of the Pakistan government but is still disputed by Bhutto's party, which maintains she was shot.
Despite the Bhutto party's support base among Pakistan's rural poor - particularly in her native Sindh province where Thatta is located - fear over rising militant violence and apathy over the nation's elitist politics has dampened public enthusiasm for the election.
The result remains hard to call because of an absence of reliable opinion polls and opposition allegations that the vote will be rigged.