The move came as a bomb outside a candidate's office wounded nine people - the second attack on a politician in two days in a country that is still reeling from the assassination of opposition leader Benazir Bhutto in December.

In a show of force ahead of Monday's polls, army soldiers and paramilitary forces stood guard at government buildings and potentially sensitive areas of several major cities, witnesses said.

'Army has started mobilising and moving to their respective areas of deployment today and would complete its deployment by February 15,' interior ministry spokesman Javed Cheema told reporters.

Authorities had drawn up plans to provide security for more than 64,000 polling stations, Mr Cheema said. More than 1,000 international observers and journalists were coming to monitor the polls, he added.

He rejected opposition concerns that the army could be used to interfere with the polls to benefit allies of President Pervez Musharraf - a former general who only quit the army in November.

'All these arrangements have been made to ensure that people cast their vote without any fear in an environment of peace and order. Nobody would be allowed to disrupt the polling process or create any law and order situation,' he said.

Officials in southern Sindh province - Bhutto's political powerbase - said they had asked the army for four helicopters for surveillance duties and recruited 15,000 'volunteers' to assist police.

'We have also provided security to some political personalities including (Bhutto's husband) Asif Ali Zardari who have threats to their lives,' provincial home minister Akhtar Zamin said.

Pakistan has been hit by a wave of bombings in the run-up to the elections, most notably the attack at a political rally on December 27 that killed former premier Bhutto.

The government has blamed an Al-Qaeda-linked tribal warlord for her murder and a series of bombings that have left around 100 people dead this year. It has warned candidates that they are at risk of attack.

A bomb attached to a bicycle exploded outside the office of an election candidate during a press conference in the southwestern town of Khuzdar on Tuesday, wounding nine people including four journalists, police said.

The candidate, Sardar Aslam Bizenjo, was unhurt, they said.

A suicide car bomber killed several people in an attack on an election candidate's convoy in a northwestern tribal town on Monday.

But after a lacklustre start to the election campaign, Mr Zardari and other political leaders are scheduled to address big rallies later this week.

Mr Zardari, former prime minister Nawaz Sharif and other opposition politicians have all accused the government of making efforts to rig the polls, the first in Pakistan for nearly six years.

Human Rights Watch warned in a statement on Tuesday that Pakistan's Election Commission had failed to investigate reports of campaign violations, threatening the validity of the polls.

The New York-based group said the commission had ignored reports of arrests and harassment of opposition members, and failed to act independently from Mr Musharraf's administration.

'There have been numerous complaints of improper government assistance to the ruling party and illegal interference with opposition activities,' said Mr Brad Adams, the group's Asia director.

'But the Election Commission has done nothing significant to address these problems, raising serious questions about its impartiality.'

Two surveys released on Monday by US-based groups found that Bhutto's Pakistan People's Party was the most popular in the country and that support for Musharraf and his allies had plummeted. -- AFP