Pakistan cricket hero turned politician Imran Khan claimed victory Thursday in the country's tense general election, following accusations of "blatant" vote-rigging by rival parties.

There was no official confirmation of results from Pakistan's election commission almost 24 hours after polls closed in Wednesday's vote but partial, unofficial tallies showed Khan's Pakistan Tehreek-e-Insaf (PTI) party enjoying a clear lead.

"We were successful and we were given a mandate," Khan, 65, said during a live broadcast, adding that there was "no politician victimisation" in the acrimonious contest.

He went on to call the elections the "most transparent" in the country's history.

During the broadcast, Khan vowed to tackle corruption that was "eating our country like a cancer".

He also touched on promises to balance relations with the US that would be "beneficial" for both countries.

Khan's statement came several hours after his supporters took to the streets to celebrate winning elections.

The unprecedented delay in counting votes, along with a surprisingly strong lead for Khan, have fuelled widespread fears over the legitimacy of the exercise.

Newspapers and television channels have been predicting victory for PTI since late Wednesday. By Thursday partial, unofficial results gave him at least 100 seats so far in the National Assembly, the lower house.

A majority of 137 seats is needed to form a government.

Khan's ex-wife, British film producer Jemima Goldsmith, tweeted her congratulations.

"22 years later, after humiliations, hurdles and sacrifices, my sons' father is Pakistan's next PM," she wrote.

The Election Commission of Pakistan dismissed allegations of manipulation, blaming the delay on glitches in new, untested counting software.

"These elections were 100 percent fair and transparent," said Chief Election Commissioner Sardar Muhammad Raza early Thursday as the outcry grew.

Election authorities have not yet confirmed when they expect to announce the results. Some reports suggested it would not be until Thursday evening at the earliest.

Election observers including a mission from the European Union are due to give their own observations on the voting process on Friday.