MINSK, Belarus — He bungled the coronavirus pandemic, alienated his longstanding foreign ally and last week faced the biggest anti-government protests in decades, but on Sunday, President Aleksandr G. Lukashenko of Belarus was on course to win his sixth term in office, in an election his critics dismissed as rigged.
According to a government-sponsored exit poll released after voting ended, Mr. Lukashenko won just under 80 percent of the vote against four rivals, avoiding a runoff vote.
A heavy cloak of security descended over the capital, Minsk, where internet service was cut off, phones worked only sporadically and soldiers and riot police cordoned off the central square and the main public buildings. Long before the results were announced, the opposition, predicting that the count would be illegitimate, had called for protests on Sunday night.
Tension escalated sharply Sunday evening after a police truck rammed into a crowd of protesters blocking a major avenue in the center of the capital, injuring several people. The protesters had barricaded the avenue with metal dumpsters but were eventually dispersed by squads of riot police officers.
The downtown area vibrated with the din of stun grenades as security forces, backed by water cannons, moved in to break up crowds of opposition supporters who gathered throughout the evening in locations across the city.
“I don’t know who voted for him, how could he get 80 percent?” said Dmitri, 25. Like many people here, he refused to give his last name for fear of repercussions.
The result of the vote, as in previous elections, was never in any real doubt: Mr. Lukashenko controls vote counting, a vast security apparatus and a noisy state media machine unwavering in its support for him and contempt for his rivals. Facing the biggest outpouring of dissent during his 26 years of autocratic rule, he hoped to return his restive country to the predictable political rhythms that have kept him in power.
“Nothing will get out of control. This I guarantee,” Mr. Lukashenko said on Sunday, warning that anyone seeking to upset stability “will receive an immediate response from me.”
Security services arrested hundreds of protesters and many journalists in recent days, and on the eve of voting, the principal challenger, Svetlana Tikhanovskaya, went into hiding in Minsk after security agents detained at least eight members of her campaign staff. The exit poll showed her in second place, with less than 7 percent of the vote.
Thousands of opposition supporters also gathered on Sunday night near a war museum in Minsk to contest the apparent election results, and security officers detained dozens of them. Protesters blocked a nearby avenue, with police officers firing stun grenades in an effort to dislodge them.
Ms. Tikhanovskaya had entered the race after her husband, Sergey Tikhanovsky, a popular blogger and would-be presidential candidate, was arrested and thrown in jail on what were widely viewed as trumped-up financial charges.
Mr. Lukashenko, unfazed by criticism of widespread pre-election repression, radiated confidence as he cast his vote at a university in Minsk on Sunday morning.
“They aren’t even worth repressing,” he said of his opponents. “To be honest, we have been soft so far. I can tell you honestly, we have always restrained the law enforcement.”
The opposition, energized by weeks of protests but unable to break Mr. Lukashenko’s tight grip on the electoral system, dismissed the election as blatantly rigged.
Despite the foregone nature of the election outcome, Mr. Lukashenko had been challenged like never before this year, amid the biggest surge of public discontent since he won the presidency for a first time in 1994, the last election in Belarus that outside observers judged to be reasonably free and fair.
He has struggled with a faltering economy, anger over his handling of the coronavirus pandemic, which he denied posed any threat to health, defections by members of the country’s economic and political elite and an open rift with his longtime ally and benefactor, President Vladimir V. Putin of Russia.
A former collective farm manager, Mr. Lukashenko enjoyed genuine support at the start of his rule, appealing to voters by preserving many aspects of the Soviet-era economy, including a large but inefficient state-owned industrial sector. This allowed Belarus, a country of about 9.5 million people, to avoid the chaos endured by former Soviet states like Russia and Ukraine in the 1990s, when a few, aided by cronyism and corruption, built vast fortunes, and millions of others were plunged into poverty.
But his policies have grown increasingly unpopular as the Belarusian economy failed to grow and modernize. (Valery Tsepkalo, the architect of the country’s only significant economic success, a high-tech development zone in Minsk, broke with Mr. Lukashenko and had planned to run against him in Sunday’s election. But Mr. Tsepkalo, warned that he, too, would soon be arrested, fled to Russia last month.)
With Russia increasingly reluctant to bankroll Belarus through cut-price oil deals, the economy has gone into steep decline and with it Mr. Lukashenko’s popularity.
His already souring relations with Moscow took a bizarre new turn for the worse last week when his security services arrested 33 Russians, accusing them of being part of a team of mercenaries sent to Belarus to disrupt the election. A few days later, the authorities also took a swipe at the United States, saying that several suspicious Americans had been arrested, too.
For outside observers, there was little question about the election’s legitimacy. More than 41 percent of voters cast their ballots before Sunday. The only international observers in the country were from Russia, Azerbaijan and a few other countries with questionable democratic records.
Ms. Tikhanovskaya, who was declared the united opposition candidate in July after Mr. Lukashenko’s other strong opponents were either arrested or forced to flee, fled her apartment in Minsk on Saturday evening and went into hiding but emerged briefly on Sunday to vote. She feared arrest, her campaign said, after plainclothes security officers appeared near her apartment building and a riot police van parked nearby.
Many journalists were denied accreditation to cover the elections. On Sunday, a reporter and cameraman from TV Rain, an independent Russian television station, were arrested in central Minsk. Three other journalists from the Current Time news outlet, which is affiliated with Radio Free Europe, were detained on Friday and expelled from the country.
As the end of voting neared on Sunday, the security services mobilized in a futile effort to prevent any postelection protests. Army vehicles, police riot vans and water cannons appeared on streets in Minsk and checkpoints were set up at entrances to the capital.
In the days preceding the vote, riot police and plainclothes officers of the main security agency, still known by its Soviet-era name, the K.G.B., grabbed protesters off the streets. On Friday, several Telegram channels, where all protest activities are coordinated, called on opposition activists to ride bicycles in the city center in Minsk. Many bike riders were arrested and pushed into police vans together with their bikes.
On Sunday, local authorities jammed access to main social networks. Twitter and Telegram could not be loaded in central Minsk, where many stores stopped accepting card payments in the absence of a stable internet connection. People lined up in front of bank machines to get cash for the coming days.
During voting on Sunday, state-run television campaigned energetically in favor of Mr. Lukashenko, broadcasting interviews with pop singers and other popular figures praising the president and speaking in favor of “stability and gradual development” as opposed to revolution.
Lidya M. Yermoshina, the head of the Central Electoral Commission, a government body, accused opposition supporters of behaving like members of a fringe religious group.
“They are so ubiquitous, they work like a banned sect,” Mrs. Yermoshina, who has headed the commission since 1996, said in an interview, broadcast by Belarus-24, a government-owned news network. “They approach people on the streets, they accost people at entrances to polling stations.”
Ivan Nechepurenko reported from Minsk, Belarus, and Andrew Higgins from Moscow.