ISLAMABAD, Pakistan — Nearly half of Pakistanis surveyed suspect that government agencies or government-linked politicians killed Benazir Bhutto, according to an opinion poll, highlighting popular mistrust in the country’s American-allied president ahead of elections next month.

Bhutto, an opposition leader and former prime minister, was killed in a gun and suicide bomb attack on December 27 that the government of President Musharraf has blamed on Islamic extremists.

Bhutto, who had been threatened by militants before, was a secular politician popular in America and other Western countries for her vocal opposition to hard-line Islam.

Her political party and family members have accused the government of failing to provide her with sufficient security, contributing to her death, and some have made vague allegations that elements within Mr. Musharraf’s government may even have been involved.

Mr. Musharraf has denied any role in the slaying, and there have been no specific claims of responsibility for her death.

Separately, Islamic militants attacked a Pakistani military base near the Afghan border, sparking fighting that killed between 40 and 50 insurgents in some of the deadliest clashes in weeks in the lawless region, the army said yesterday.

The army said up to 300 militants staged the attack in Lhada on Wednesday and early Thursday, but were repelled by artillery and small-arms fire.

The opinion poll asking who “killed” Bhutto, released Saturday, indicated that 23% of Pakistanis suspected government agencies in the slaying, while 25% believed government-allied politicians were behind it. Only 17% suspected Al Qaeda or Taliban.

The poll by Gallup Pakistan, which is affiliated with the Gallup International polling group, questioned 1,300 men and women in face-to-face interviews across Pakistan soon after Bhutto’s slaying. It had a margin of error of 5 percentage points.

Information Minister Nisar Memon questioned the poll and its findings.

“I don’t think this is representative of the thought process of the people of Pakistan, and neither does it reflect the realities,” he said of the survey. “It is very clear that people know that it is the terrorists who are responsible.”

Mr. Musharraf, who has himself survived at least three assassination attempts blamed on militants, seized power eight years ago in a military coup. His popularity was already low before the Bhutto assassination amid demands for greater democratic rule.

The parliamentary elections, which will take place on February 18 after being delayed for six weeks amid rioting triggered by Bhutto’s death, are seen as key to Pakistan’s transition to democracy.

Bhutto’s party and the other major opposition grouping are expected to do well, in part because of sympathy over her death. But most analysts expect no party will gain enough seats to form a government alone and predict the election will result in a likely unstable coalition. Others fear that vote-rigging may taint the process and trigger fresh disputes.

Allegations of state involvement in Bhutto’s death have been fueled by apparent government inconsistencies over precisely how she died.

Video footage shows a man firing at her from close range as she pokes her head through the sunroof of her vehicle. Seconds later, the car is struck by a large explosion.

The government initially said she died when the force of the blast propelled her head into the sunroof of her vehicle.

Her supporters say she was shot dead, as some video footage of the incident appears to support.