LAHORE, Pakistan — Imran Khan, a cricket legend and conservative politician, appeared to be leading late Wednesday in national parliamentary elections where he is the main challenger to the ruling Pakistani Muslim League-N and the wealthy Sharif family that has dominated Pakistani politics for the past two decades.

About four hours after the polls closed, partial unofficial results reported by numerous TV news channels showed Khan and other candidates in his Pakistan Justice Movement leading in contests for between 85 and 100 seats, while Muslim League candidates were reported leading in races for between 50 and 38 seats, and other parties trailed behind.

No official results were expected until late Thursday morning, but Khan’s youthful supporters were shown on TV news clips singing and dancing in celebration in various cities and towns, and Khan’s aides said they expected him to speak later in the night. His party would need to win 141 of 272 seats to form a government on its own but would be more likely to form a governing coalition with other parties.

The partial results came after millions of voters turned out despite a bomb blast near a polling station that took at least 29 lives and a campaign marked by rancor, terrorist attacks, accusations of military meddling, and the dramatic return of former prime minister Nawaz Sharif to serve a prison term for financial misdeeds.

The polls were heavily guarded by a combination of police, troops, and paramilitary rangers, after several attacks over the course of the campaign that killed more than 200 people. The attacks included a suicide bombing at a rally in northwestern Khyber Pakhtunkhwa province that killed Haroon Bilour, a leader of the Awami National Party, and a blast in southwestern Baluchistan province that killed 145 people, including a candidate for Parliament.

Despite the intensified security after the spate of campaign-related violence, a suicide bomber struck Wednesday morning near a polling station in Quetta, the capital of Baluchistan, killing at least 29 people and wounding 40, officials said. The bomber tried to enter the voting facility on foot but set off his load when security personnel stopped him, officials said.

Several hours later, army officials posted online a photo of General Qamar Javed Bajwa, the army chief of staff, casting his vote in Rawalpindi, the city where the army headquarters is located. It was accompanied by a quote from Bajwa saying that ‘‘inimical forces’’ are working against Pakistan and that ‘‘we are united and steadfast to defeat them.’’ He urged Pakistanis, ‘‘Please come out and vote undeterred.’’

The hotly contested election marked only the second democratic transition of power since the end of 17 years of military rule in 2008, with more than 105 million people eligible to vote at 85,000 voting stations nationwide. The decisive battle was in and around Lahore, the capital of wealthy Punjab province, where the Sharif family has dominated politics for several decades.

Both Khan and Shahbaz Sharif, the younger brother of Nawaz Sharif, are running for Parliament from Lahore, and one or the other is likely to become prime minister if his party scores a significant victory. Their rivalry embodies two competing versions of reality — Khan’s call to free Pakistan of corrupt political dynasties, and the Sharifs’ call to free Pakistan of shadowy military, judicial, and bureaucratic influence in politics.

Regardless of whether Khan, with his legions of youthful grass-roots followers, is able to defeat the troubled Muslim League, analysts predicted that neither party would win enough votes to form a government, leading to a period of weak coalition rule with the Pakistan People’s Party, or possibly a hung Parliament, with the military exercising more power behind the scenes.

Nawaz Sharif was disqualified from public office by the Supreme Court last year, after hearings on charges of financial misdeeds that were pushed by Khan and others. Sharif claimed he was the victim of hidden pressure from the military and its allies in the civilian establishment. During the campaign, there were widespread reports that such pressure had prompted dozens of Muslim League candidates or rising figures to leave the party.

‘‘Despite being imprisoned, I am witnessing your passion and listening to your chants to respect the vote,’’ Sharif said Wednesday in a message to supporters from Adiala Jail in Rawalpindi. In the message, relayed through the Twitter handle of his daughter Maryam Nawaz, who is also in jail, Sharif urged voters to give ‘‘one final push to break the wall’’ of hidden official opposition to democracy.

Khan, in tweets on Tuesday after a frenetic campaign that included appearances at 60 rallies, said, ‘‘This has been the culmination of 22 years of struggle. I can honestly say I have given my best for Pakistan. The rest is up to Allah.’’ He urged people to come out and vote, tweeting, ‘‘This is the first time in 4 decades the nation has a chance to defeat the entrenched status quo. Don’t miss this opportunity.’’

In several Lahore districts, some voters said they were touched and inspired by Sharif’s decision to return home from London to face jail, leaving behind his wife, who is hospitalized with a serious illness. One, a shopkeeper named Raees Ahmed, said, ‘‘He could have easily lived in London, but he came for us, for democracy and for civilian supremacy. He has done his job, and it’s our turn now to do ours.’’