ISLAMABAD, PAKISTAN - PAKISTANI security forces were on their highest state of alert on Sunday after a suicide car bomber killed 37 people and wounded nearly 100 at a rally for next week's critical parliamentary elections.

The government stepped up security for Monday's polls after the final day of campaigning was marred by the deadliest attack since the assassination of former premier Benazir Bhutto late last year.

Nuclear-armed Pakistan has seen a wave of suicide attacks since Ms Bhutto was killed in a suicide and gun attack at a political rally in Rawalpindi, casting doubt over the authority of key United States ally President Pervez Musharraf.

'Polling stations will be fully secured, the security of the voters will be ensured at all costs.

'We know there are elements who are trying to sabotage the entire process but we will defeat their designs - we are determined to do so.'

Saturday's blast, the latest in a series of attacks that have rocked Pakistan's shaky electoral process, occurred at a rally for Ms Bhutto's Pakistan People's Party in the north-western tribal town of Parachinar.

Hours later, a second suicide car bomber attacked an army media centre in the troubled north-western region of Swat, killing two civilians and wounding eight other people.

Saturday's attacks came as politicians launched a final push for votes before the midnight (3am Singapore time) deadline after which all rallies are banned until the polls close.

Ms Bhutto's widower, Mr Asif Ali Zardari, met former premier Nawaz Sharif in Lahore on Saturday for new talks on possible power-sharing after the vote if the opposition wins a majority, party officials said.

Monday's poll has been overshadowed by the wave of violence, and dogged by widespread allegations of rigging in favour of Mr Musharraf's allies.

Mr Musharraf, who sacked the judiciary last year to pave the way to a second presidential term, is not contesting the polls, but he faces impeachment if the opposition wins more than two-thirds of Parliament.

The White House, which counts embattled Mr Musharraf as a bulwark against Al-Qaeda and Taleban militants, moved to dispel fears that violence could derail the vote.

'We want to see an election in which all the parties can compete fairly. Violence is not the answer, and we know this latest attack will not stop the people of Pakistan from voting,' White House spokesman Gordon Johndroe said.

Some 81,000 army and paramilitary soldiers have fanned out across the country to try to maintain peace and security during the election.

But the blast at the PPP rally and a series of other incidents at the weekend highlighted Pakistan's perilous security situation.

Militants in the tribal region of Bajaur blew up a polling station on Saturday, while police in the southern city of Hyderabad said they had arrested three suspected militants equipped with suicide jackets who were planning an attack during the polls.

And in the south-western city of Quetta police fired tear gas and used batons to disperse a rally by a coalition of opposition parties boycotting the elections. -- AFP