Imran Khan declares victory in Pakistan election marred by vote-rigging accusations

Pakistan cricket hero turned politician Imran Khan claimed victory on Thursday in the country's general election, in a poll marked by violence and accusations of vote-rigging by rivals.

Partial and unofficial tallies showed Khan's Pakistan Tehreek-e-Insaf (PTI) party enjoying a clear lead, despite no official confirmation of results from Pakistan's election commission almost 24 hours after polls closed on Wednesday.

"We were successful and we were given a mandate," Khan, 65, said during a live broadcast.

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

Khan's statement came several hours after his supporters took to the streets to celebrate winning an election that opponents have said the powerful military rigged in his favour.

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.

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.

The military, which had been accused of seeking to manipulate the vote in Khan's favour in the months leading up to the polls, has not yet commented on the situation. It and Khan have previously denied allegations of intervention.

Late Wednesday, the once-mighty Pakistan Muslim League-Nawaz (PML-N), which had been in power since 2013, rejected the results because of "outright rigging," and vowed it would use "all political and legal options for redressal of these glaring excesses".

Other major parties also alleged fraud, including the left-wing Pakistan Peoples Party (PPP).

The size of Khan's lead against the PML-N, when many analysts had predicted a coalition would be likely, was also increasing concern over the process.

At least one party - Tehreek-e-Labaik Pakistan (TLP), which blockaded the capital Islamabad for weeks last year over blasphemy - has already announced it is planning protests.

The controversy over the vote follows a campaign already considered by some observers to be one of the "dirtiest" in Pakistan's history.

Wednesday's elections were meant to be a rare democratic transition from one civilian government to another in the young, nuclear-armed country which has been ruled by the military for roughly half its history.

Khan, who captained Pakistan to their World Cup cricket victory in 1992, was dogged by the accusations he was benefiting from a "silent coup" by the generals which targeted the PML-N. Nawaz Sharif was ousted from power last year and jailed over a corruption conviction days before the vote, removing Khan's most dangerous rival.

The military has also stationed over 370,000 personnel across Pakistan to what it says ensure security for the election, bolstered by an additional 450,000 police.

But a blast at a polling station in the restive Balochistan province, Pakistan's poorest, which is plagued by Islamist and separatist insurgencies, left at least 31 dead on Wednesday.

The contest has largely become a two-way race between PTI, and the incumbent PML-N of ousted premier Nawaz Sharif, whose brother Shahbaz is leading its campaign.

Khan has also increasingly catered to Islamist groups, sparking fears a win for PTI could embolden hardliners.

Agencies contributed to this report.