Pakistan's former cricket star Imran Khan and his party Pakistan Tehreek-e-Insaf (PTI) are maintaining a commanding lead amid slow and tedious counting of ballots from Wednesday’s election that has been marred by allegations of fraud and militant violence.

By 3pm Kabul time, Pakistani election officials said an official count confirming Pakistan's next government was expected later in the evening.

AP reported that before even half the votes were counted, Khan's leading rival Shehbaz Sharif, who heads the Pakistan Muslim League-Nawaz (PML-N) - the party of jailed ex-prime minister Nawaz Sharif - rejected the vote, generating fears that disgruntled losers could delay the formation of the next government.

But Pakistan media reported former Pakistan president Pervez Musharraf said the results were "realistic” and he rejected charges of poll rigging.

"I certainly won't (pay heed to the allegations of poll rigging), because I think this is bad habit with those who lose here. They always start cribbing that there has been rigging. I don't think there has been rigging. The results are very realistic," he said.

Pakistan media also reported that former Pakistan prime minister Shahid Khaqan Abbasi, his party president Shehbaz Sharif and chief of the Jamat-i-Islami Sirajul Haq were among the stalwarts who suffered a shocking defeat in the general elections.

But despite the electoral chaos and the outgoing ruling party denouncing the polls, partial results have suggested Imran Khan the winner.

Results are still being tallied however, manually, hours after Khan's supporters took to the streets to celebrate.

The unprecedented delay in releasing election results has meanwhile fueled widespread fears over the legitimacy of the exercise.

According to AFP, newspapers and television channels are predicting victory for Khan's Pakistan Tehreek-e-Insaf, with the partial results giving 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.

This election will mark only the second civilian transfer of power in Pakistan's 71-year history, and comes at a time when relations with on-off ally the United States are volatile.

But campaigning has been plagued for months by allegations that powerful armed forces have been trying to tilt the race in Khan's favor after falling out with the outgoing ruling party of Sharif, who was jailed on corruption charges this month.

Election results were due to have been released by 2am Thursday but at 3am Pakistan’s Election Commission issued the following statement. “Result Transmission Service stopped working under pressure & has delayed results.”