An official result has not yet been announced
Former cricket star Imran Khan has promised to build a "new" Pakistan after declaring victory in the country's general election.
The leader of Pakistan's Tehreek-e-Insaf party gave a live-televised address, a day after tens of millions of people cast their ballots in an election marred by violence.
An official result has not yet been announced following delays in counting and allegations of vote rigging.
Votes were still being counted on Thursday, hours after Mr Khan's supporters took to the streets to celebrate his expected win.
"We were successful and we were given a mandate," Mr Khan said.
"All our policies will be focused on bringing up the poorest segment of society.
"No political leader has ever been a victim of as many personal attacks as I have over the last few years but our mission is much bigger than me.
"I say to the people of this country today, we will govern Pakistan like it has never been governed before."
The result had been due by 2am local time (10pm Irish time) on Wednesday - but election officials said it will be Thursday evening before the official count is confirmed, blaming technical problems.
About half the votes had been counted more than 17 hours after polls closed, local media reported.
The Pakistan Muslim League-Nawaz (PML-N), the party of jailed ex-prime minister Nawaz Sharif, has called the count an "assault on democracy" in a country which has a history of military rule.
Violence has marred the election, with a suicide bombing outside a polling station in the city of Quetta on Wednesday killing at least 31 people - including five policeman and two children.
Terror group Islamic State claimed responsibility for the attack.
Election official Babar Yaqoob said counting had been delayed by technical failures in an electronic reporting system and the tallying was now being conducted manually.
"There's no conspiracy, nor any pressure in delay of the results," he said.
"The delay is being caused because the result transmission system has collapsed."
Mr Sharif's brother Shehbaz, who nows leads the PML-N, rejected the vote, calling it "sheer rigging".
"The way the people's mandate has blatantly been insulted, it is intolerable," he said.
"We totally reject this result. It is a big shock to Pakistan's democratic process."
In his address, Mr Khan said: "If parties are saying there has been vote rigging, they should name the polling stations and we will open an investigation."
His former wife, broadcaster Jemima Goldsmith, tweeted her congratulations ahead of the official result.
22 years later, after humiliations, hurdles and sacrifices, my sons’ father is Pakistan’s next PM. It’s an incredible lesson in tenacity, belief & refusal to accept defeat. The challenge now is to remember why he entered politics in the 1st place. Congratulations @ImranKhanPTI— Jemima Goldsmith (@Jemima_Khan) July 26, 2018
It appears likely Tehreek-e-Insaf will fall short of the 137 seats needed to form a government, raising the prospect Mr Khan's party will have to find coalition partners.
If successful, the elections will mark only the second time a civilian government has handed power to another in Pakistan since the country's independence in 1947.
The military stationed more than 370,000 personnel across Pakistan to improve security on polling day, bolstered by an additional 450,000 police.