He said the tallying was now being conducted manually. The results had been due by 2am (2100 GMT).
"These elections were 100 percent transparent and fair", Raza said.
The elections are being held as emotions run over a graft case that led to the imprisonment of ousted Prime Minister Nawaz Sharif and his daughter Maryam Nawaz. "This isn't about winning seats or forming the [provincial] government, it is about the future of this country", Shehbaz Sharif said. The PTI has won 76 of the 272 seats and is leading in 43.
Khan's Pakistan Tehreek-e-Insaf, or Movement for Justice, said it has emerged as the single largest party and can form the federal government, Naeem ul Haq, a PTI leader told reporters on Thursday in Islamabad as long-delayed counting continued.
Pakistan is ready to improve its ties with India, Pakistan Tehreek-e-Insaf chief Imran Khan said today, asserting that the blame game between the two neighbours, detrimental to the sub-continent, should stop. In 2004, the couple announced they had divorced amicably, ending the nine-year marriage because it was "difficult for Jemima to adapt to the political life of Imran Khan in Pakistan".
Jubilant Khan supporters danced to the beat of drums at his party headquarters in Islamabad, sensing a victory.
Youthful supporters of Mr Khan, who campaigned relentlessly against political corruption and elitism, sang and danced in cities and towns across the country all evening, celebrating what some called a new day in Pakistani political leadership, free of corruption and dedicated to the public good.
Radical groups such as the Milli Muslim League linked to Hafiz Saeed, the man accused of masterminding the 2008 Mumbai attacks, also contested the polls, though many are running under the banner of smaller, lesser-known parties.
Khan has been an outspoken critic of the US -led war in neighboring Afghanistan and of USA drone strikes against militants in Pakistan.
PTI leads in Pak election 2018 results
A concern is the unprecedented participation of radical religious groups, including those banned for links to terrorism but resurrected under different names.
He is also widely believed to be backed by the army, which fell out with Nawaz Sharif, who looked to curb the military's traditional dominance in politics.
An earlier attack in the province on Wednesday left one policeman dead and three wounded when a hand grenade was thrown at a polling station in the village of Koshk, in Khuzdar district.
In other areas, it said, "polling staff appeared to be biased toward a certain party", without naming the party.
Husain Haqqani, a former Pakistan ambassador to the USA, said that the result of the election was "foretold".
Despite the intensified security, another suicide bomber struck on Wednesday morning near a polling station in Quetta, the capital of Balochistan, killing 31 people, officials said. Islamic State claimed responsibility. Voting for two seats was postponed after one candidate died during the campaign and another was disqualified.
These elections are the second in Pakistan's history in which a government was able to complete its term to make way for another government after being ruled by military dictators for half of the 71 years of its existence since its founding in 1947. Final results are expected early Thursday.
The remainder in the 342-seat lower house of parliament included reserved seats for women and minorities. The ECP rejected the "blatant" rigging allegations. Sharif has clashed repeatedly with the military over the years and was jailed this month on corruption charges, which he is appealing.
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