ISLAMABAD, Pakistan - President Pervez Musharraf pledged Thursday that next week's parliamentary elections would be free, fair and held on time, after political opponents accused him of planning to rig the vote so he could maintain his grip on power.

He vowed to deal sternly with anyone who tried to disrupt the electoral process and questioned the accuracy of opinion polls that said support for his ruling party was at an all-time low.

"Despite all rumors, insinuations and every type of apprehension, these elections will be free, fair, transparent and peaceful,'' Musharraf told a gathering of intellectuals in the capital, Islamabad.

The retired army general, who seized power in a 1999 coup and went on to become a key U.S. ally in the war on terrorism, has said Monday's vote was a crucial step in the country's transition to democratic rule.

His presidency is not being contested but if his party loses control of Parliament, he could be vulnerable to impeachment.

That has sparked rumors that the government may seek an excuse to delay the vote or annul the results.

There also are fears about security in the wake of the Dec. 27 assassination of former Prime Minister Benazir Bhutto and a string of suicide bombings blamed on Islamic militants, some targeting campaign rallies. The army said an attack on one of its convoys in the volatile northwest Thursday left three soldiers dead.

Ex-Prime Minister Nawaz Sharif, a leading opposition politician, was among those who accused Musharraf of planning to rig the election.

"We stand for democracy. He stands for dictatorship,'' Sharif said as he traveled in his armor-plated SUV to a raucous campaign rally on Wednesday attended by about 7,000 supporters in the northern town of Kahuta. "In order to survive, he has to rig the election. He knows that.''

He accused the government of buying votes and readying 1.8 million postal ballots to be cast in favor of the ruling party -- allegations denied by officials -- and warned that efforts to manipulate the polls would lead to "uncontrollable'' unrest.

Opposition parties have threatened to launch street protests if the election is rigged -- something Musharraf warned against Thursday.

"We don't know who is going to lose and who is going to win,'' he said. "It is wrong. There will be no rigging.''

A survey released this week by the U.S. government-funded International Republican Institute said half the Pakistanis polled planned to vote for Bhutto's party, 22 per cent backed Sharif's group and only 14 per cent favored the ruling PML-Q.

The poll of 3,845 adults was conducted Jan. 19-29 and has a margin of error of plus or minus about 2 percentage points.

Musharraf questioned the authenticity of such surveys and criticized those carrying them out, saying "don't create problems for us.''

He also asked the media to refrain from taking sides.

The bomb Thursday struck near a military convoy heading from a post along the Afghan border to Khar, the main town in the Bajur tribal area, army spokesman Maj. Gen. Athar Abbas said. Three soldiers were killed, he said.

No one immediately claimed responsibility for the bombing.