Millions of voters brave the threat of violence to cast their vote in Monday's critical elections.
Pakistanis cast their ballots Monday in critical elections overshadowed by violence and fears of rigging, with the fate of key US ally President Pervez Musharraf hanging in the balance.
The parliamentary polls come after a year of political turmoil and bloodshed in the nuclear-armed Islamic republic, capped by the assassination of former prime minister Benazir Bhutto in a suicide attack in December.
The vote is supposed to complete Pakistan's transition to democracy after eight years of Musharraf's rule, but analysts say it is more likely to spark fresh unrest if opposition parties claim the vote is fraudulent.
Tens of thousands of troops guarded polling stations as they opened at 8:00 am, (0300 GMT). They are due to close at 5:00 pm, with the first results at about 10:30 pm.
"I am scared because of all the bombings but I am sure Allah will protect me and all the people voting today," Saima Zahoor, a housewife clad in an all-covering burka, told AFP at a polling station in the northwestern city of Peshawar.
Shortly before voting started two bombs went off at polling stations in the troubled northwestern Swat region, where troops are battling Islamic militants, causing damage but no casualties, police said.
Musharraf's spokesman Major General Rashid Qureshi dismissed opposition allegations of rigging, saying that even the ballot boxes were transparent and fitted with special seals.
"I have no doubt in my mind that the elections will be free, fair and transparent," Qureshi told AFP.
"As spokesman for the president, I have seen the earnestness with which he has been working and trying to remove every hitch for these polls," he added.
The outcome of the vote will be watched avidly in Western capitals amid concerns about Musharraf's ability to tackle Al-Qaeda and Taliban militants based in Pakistan's tribal areas on the Afghan border.
Musharraf, who seized power in a coup in 1999 and stepped down as army chief in November, is not standing in the polls, but could be badly weakened or even impeached if the public install a hostile parliament.
Bhutto's widower Asif Ali Zardari and former prime minister Nawaz Sharif have pledged to hold protests if they suspect foul play. Both have said they suspect "massive" rigging in favour of Musharraf's allies.
Opinion polls have tipped Bhutto's Pakistan People's Party to win, followed by Sharif's grouping, with the pro-Musharraf Pakistan Muslim League-Q trailing in third place.
They have also showed Musharraf's popularity slumping. But security fears after Bhutto's death - which forced the postponement of the polls from their original date on January 8 - have raised the possibility of a low turnout that would benefit Musharraf's allies.
Zardari warned in an interview with Britain's Sunday Times newspaper that he would have "no choice but to take to the streets" if the polls were fraudulent.
Sharif, Bhutto's former rival, told reporters Sunday that it was "more than clear that a massive rigging plan is in place."
One person was killed and six others wounded when gunmen riding a motorbike opened fire on an election office of a candidate for Sharif's party in the eastern city of Lahore late Sunday, police said.
The government has deployed 500,000 troops for the vote and the aftermath, including 81,000 soldiers - one for every 1,000 members of the 81-million-strong electorate.
The violence knocked the wind out of Pakistan's normally colourful electoral campaigns and added to widespread public discontent about rising prices and shortages of flour and other essentials.
Campaigning ended grimly on Saturday when a suicide car bomber ploughed into a meeting of Bhutto's supporters in the northwestern tribal town of Parachinar, killing 47 people and wounding more than 100.
The attack highlighted the Pakistani military's ongoing struggles in the tribal belt, which has been branded by US officials as a "safe haven" for Al-Qaeda militants.
Musharraf has accused a top Al-Qaeda militant based in the region of masterminding Bhutto's assassination.