PTI leader Hassan Naeem, while speaking to Geo News, said the party's tally will cross the halfway majority mark, that is 136, when the Election Commission of Pakistan (ECP) declares the final verdict.
In an effort to increase voter participation, the Election Commission has declared a public holiday on Wednesday.
The PML-N, on the other hand, says it is the target of the alleged military machinations, with candidates under pressure and Nawaz Sharif ousted from power previous year and jailed over a corruption conviction days before the vote, removing Khan's most unsafe foe from the race.
The Pakistan Tehreek-e-Insaf (PTI) of former cricket hero Imran Khan was well ahead of other parties as unofficial results poured in from across Pakistan after the day-long polling, marred by a deadly suicide bombing, closed at 6pm. First results are expected early Thursday.
Punjab province, the country's most populous, holds 141 of the country's 272 directly elected seats, and the key to forming the government.
Asked about allegations that the Pakistan Army is meddling in the elections, the spokesperson said the USA will not comment on Pakistan's internal politics. He did not say who he believes could have rigged the polls, but allegations of manipulating the elections have been made against the country's powerful military.
Amid reports of pre-poll rigging and tampering with the process of elections, Pakistan Chief Election Commissioner Justice Sardar Muhammad Raza (retired) on Tuesday reiterated that the Election Commission of Pakistan (ECP) is committed to seeing out a free and fair Pakistan general elections 2018.
Pakistani election staff prepare election material ahead of voting.
Twitter/@Sagopaak EXPLOSION ISIS has claimed responsibility for the attack which killed at least 30 people
"We reject this result", Shehbaz Sharif said.
Earlier, one policeman was killed and three wounded in a hand grenade attack on a polling station in southwestern Balochistan, Pakistan's poorest and most restive province, local police there told AFP. "At the same time, it's unfair to conclude that democracy is a lost cause in Pakistan simply because it struggles to carry out a clean election".
PML-N spokeswoman Maryam Aurangzeb also said there had been complaints about the vote counting. The Pakistan People's Party (PPP) which had won only two NA seats in 2013 polls, is hardly being seen in the race.
Independent candidate Jibran Nasir said that Tehreek-i-Labbaik Pakistan supporters attacked a facilitation camp he had set up in Chandio Village in Karachi.
"The MQM-P's representatives were thrown out from NA-249's Salahuddin school polling station 89, and from a polling station in Gulzar-e-Hijri Metroville", alleged party's senior leader Faisal Subzwari. Ikramullah Gandapur, a candidate for PTI, and Haroon Bilour, who was standing for the secular Awami National Party, were assassinated in separate attacks in northwestern Pakistan.
A political party has to secure at least 172 seats to form the government in the 342-seat National Assembly.
As per the Election Commission, at least 3,459 candidates are in the fray for 272 general seats of the National Assembly, while 8,396 candidates are running for 577 general seats of the four provincial assemblies - Punjab, Sindh, Balochistan and Khyber-Pakhtunkhwa.
Millions of voters turned out on Wednesday despite intense heat and a campaign marked by rancour, terrorist attacks, accusations of military meddling and the dramatic return of former prime minister Nawaz Sharif to serve a prison term for financial misdeeds.
Some of those candidates belong to a new, rapidly growing anti-blasphemy movement, and others are from political groups that have been officially banned because of extremist ideologies or links to groups with violent histories.More news: Mega Millions soars to $522 million for Tuesday