Khan's camp was increasingly confident, but it still appeared likely to fall short of a clear majority in the National Assembly.
As the counting continued, projections from four local TV channels put Khan's party ahead, estimating it would win between 107 and 120 seats of 272 elected seats available, while Sharif's outgoing ruling party was estimated at between 42 and 69. However, those projections were based on only about 10-15 percent of votes counted.
Khan's party spokesman, Fawad Chaudhry, showed confidence as the early projections were broadcast, saying in a tweet "Congratulations to the nation on a new Pakistan!".
"Imran Khan is the only hope to change destiny of our country".
The PTI, led by cricketer-turned-politician Imran Khan, is looking to unseat the incumbent PML-N, which was formally led by the now jailed ex-prime minister Nawaz Sharif.
"It is a sheer rigging".
Addressing a press conference, PML-N president Shehbaz Sharif said he had received complaints of irregularities from across Pakistan, adding that other parties have also raised similar objections. "It is a big shock to Pakistan's democratic process".
For the first time in 2013, a civilian government in Pakistan completed its five-year term.
Pakistanis began voting in a historic third straight election ending a campaign marred by widespread allegations of manipulation that local and global rights group say imperils the country's wobbly transition to democratic rule.
Voting day was marred by a suicide blast that killed almost 30 people near a polling centre in Quetta, the capital of Balochistan province.
However, the day has not been without violence, as interparty violence and militant attacks have left over a dozen dead.
ISIS claims responsibility for Pakistani polling station blast
"I was going to vote for Nawaz Sharif, but the way that he lied on the floor of the House, that convinced me that I couldn't vote for him", said Ahmed Ali Malik, a retired banker who flew in from Manchester in the United Kingdom to vote at Lahore's Delhi Gate. "In the past we have seen such referendums not election", the PSP leader sarcastically remarked.
ISIS has claimed responsibility for the attack via its official news agency.
As well, Khan's vehicle was allowed to enter the polling station, and he also brought members of his party, the Pakistan Tehreek-e-Insaf, inside.
Khan cast his vote in Bani Gala, a suburb of the capital Islamabad, telling the media it was "time to defeat parties which kept this country hostage for years".
"I ask everyone today - be a citizen, cherish this country, worry about this country, use your vote".
Millions of Pakistanis vote Wednesday in a tense election marred by allegations of military interference and a series of deadly attacks, and which observers said was still up in the air.
Around 50 political and religious parties are taking part in the elections, which have been marred by allegations of "manipulation" and "engineering".
Khan's Pakistan Tehreek-e-Insaf (PTI) party has inched ahead of PML-N in recent national polls, but even if it gets the most votes, it will likely struggle to win a majority, raising the prospect of weeks of haggling to form a messy coalition government. PTI has not ruled out seeking succour from China, Islamabad's closest ally.
Sharif's PML-N has been touting its delivery of mega infrastructure projects, especially roads and power stations that helped hugely reduce electricity blackouts, as proof the country is on the path to prosperity. PTI was leading on five seats while PML-N was ahead on one.
Marriyum Aurangzeb said that if the mandate of the PML-N is "stolen", it will not be acceptable to the party's voters.
"We have serious reservations".
Meghan continues to make Canada proud with her fashion choices
In a less-than-surprising statement, she teamed the protocol-breaking look with a co-ordinating £600 clutch by Mulberry and £520 Dior shoes .