Wally Santana, Associated Press
A supporter of the Pakistan People's Party holds a portrait of slain party leader Benazir Bhutto during a campaign rally in Rawalpindi Saturday. In Parachinar, a suicide bomber appeared to target members of the Pakistan People's Party.

ISLAMABAD, Pakistan — A suicide bomber rammed a car packed with explosives into a crowd following a rally for a candidate allied with the opposition, killing 37 people and heightening fears of Islamic militant violence during Monday's crucial parliamentary elections.

Most of the victims of Saturday's attack appeared to be members of the opposition Pakistan People's Party, formerly led by the slain Benazir Bhutto. They had gathered at the home of the targeted candidate following the rally in a volatile tribal region bordering Afghanistan, said Mushtaq Hussain, an administrative official in the area.

"Several of our party members are lying in a pool of blood," said Zafar Ali, a party supporter at the scene.

The attack came two days before elections considered crucial to restoring democracy in Pakistan after eight years of military rule under President Pervez Musharraf. Recent opinion polls show the opposition poised for a landslide victory amid disenchantment with Musharraf's rule.

In addition to rising political discontent following Musharraf's decisions in the last year to impose emergency rule and purge the judiciary, he is battling a rising Islamic militancy.

In another area along the border, a second car bombing near a checkpoint killed two civilians and wounded eight security personnel, said army spokesman Maj. Gen. Athar Abbas. That blast occurred near Swat, a former tourist destination where security forces have battled armed supporters of a pro-Taliban cleric in recent months.

The candidate targeted in the first suicide bombing, Syed Riaz Hussain, was unharmed. He is backed by the opposition PPP.

The injured poured into a nearby hospital, many in critical condition with severe burn wounds, doctors said.

Interior Ministry spokesman Javed Iqbal Cheema said 37 people were killed and more than 90 wounded when the suicide bomber drove into a crowd as they were preparing to eat in the town of Parachinar.

Asked who could be behind the bombing, he said those "who want to derail the election process."

The Dec. 27 assassination of opposition leader Bhutto and a string of suicide bombings — some targeting campaign rallies — have been blamed on al-Qaida- or Taliban-linked militants.

For some, the biggest fear is major violence between political parties if there are widespread allegations of cheating.

Highlighting those tensions, hundreds of police surrounded and then clashed with more than 1,500 supporters of a coalition of anti-Musharraf parties boycotting the vote in the southwestern city of Quetta on Saturday. Seven people were injured.

The demonstrators threw rocks at police, who responded with tear gas before arresting 50 activists for the violence, said police officer Raja Mohammed Ishtiaq. A truck and three motorcycles were burned in the melee, and the street was littered with party flags and shoes.

In the northwest, suspected militants also bombed a polling station that badly damaged the building but caused no injuries.

The government has deployed 81,000 soldiers to back up 392,000 police assigned to protect voters, said military spokesman Abbas.

Musharraf said Saturday he was confident the elections would be free and fair and, hopefully, without violence.<

"We will have a stable, democratically elected government and with the stable, democratically elected government we will ensure a successful fight against terrorism and extremism," he said in a speech to diplomats and senior government officials that ran on state-run Pakistan Television.

Although Musharraf is not up for re-election, he could face impeachment if the opposition wins a two-thirds majority in the legislature.

Opposition politicians fear the results will be manipulated in hopes of assuring the ruling party enough seats to block any impeachment.

"We know very well that elections are being rigged," former Prime Minister Nawaz Sharif, one of the president's sharpest critics, told reporters at his home in the eastern city of Lahore. "We are going to elections in an environment of cheating, fear and threats."

Kanwar Dilshad, the No. 2 official in Pakistan's Election Commission, insisted there would be no rigging.

"We are neutral. A level playing field has been provided to all the contesting candidates, and we are doing our job to ensure free, fair, transparent and peaceful elections," Dilshad told The Associated Press.

Last week, New York-based Human Rights Watch questioned the election commission's impartiality, saying it has ignored complaints of harassment against opposition candidates.

On Friday, Sen. Joseph Biden, a Delaware Democrat who heads the Senate Foreign Relations Committee, said the United States should consider cutting off military aid to Pakistan if the elections are rigged.