However, early unofficial results gave cricket star Imran Khan and his Pakistan Tehreek-e-Insaf Party a commanding lead over his main rival, Shahbaz Sharif's Pakistan Muslim League. He said the tallying was now being conducted manually.
Supporters of Pakistan Muslim League-N party listen to speech of their leader during an election campaign rally in Rawalpindi, Pakistan.
Bhutto - son of slain prime minister Benazir Bhutto - and his PPP could be called upon to form a coalition with any victor. The PPP was leading in races for 42 seats.
His PTI party is still expected to fall short of an overall majority and to seek coalition partners.
Less than two weeks before polling day, Sharif returned to Pakistan from the United Kingdom to face a ten year sentence for corruption that made him ineligible from participating in politics. "Prime Minister Imran Khan".
Throughout the night and into Thursday, Khan supporters celebrated outside party offices countrywide.
Khan, a cricket legend of nearly mythical proportions, has appealed to the youth with promises of a new Pakistan.
"I remember IK's 1st election in 1997- untested, idealistic & politically naive".
Khan has been an outspoken critic of the US-led war in neighbouring Afghanistan as well as China's massive investment in Pakistan, which has racked up millions of dollars in debt to Beijing.
Khan has also criticized Pakistani liberals and embraced conservative Islam as a politician, promising a Taliban-style justice system.
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A concern is the unprecedented participation of radical religious groups, including those banned for links to terrorism but resurrected under different names. The army has also dismissed allegations of meddling in the election. "We know all the other candidates and parties".
About 371,000 soldiers have been stationed at polling stations across the country, almost five times the number deployed at the last election in 2013.
"Imran Khan doesn't have many friends or allies; he's not someone who really knows how to work with people", said Mohammad Malick, a popular political talk show host, referring to Khan's famous stubbornness.
Just under 106 million voters - half of the population - braved visits to polling stations despite an Islamic State suicide bomb killing 31 people. Islamic State claimed responsibility.
In his first press conference after declaring victory in the Pakistan elections, Pakistan Tehreek-i-Insaf chief Imran Khan on Thursday touched upon the Kashmir dispute, saying the only way to solve the decades-old crisis was through dialogue with India.
This election will mark only the second civilian transfer of power in Pakistan's 71-year history.
The military, which has ruled Pakistan for almost half of its 71-year history, denies any effort to influence the election.
Voting appeared to be heavy in major urban centers, where long lines of voters were seen.
Women were also allegedly barred from voting at some polling stations yesterday by the military, which backs anti-feminist Mr Khan.
But it hasn't addressed the issue of why the polling agents were evicted from the polling stations.
The Americans will be particularly concerned about the outcome of the election, given that Khan famously said he would order the Pakistani military to shoot down American drones if he came to power, and advocated negotiations with Pakistani Taliban fighters rather than military operations against them.