Belarusan President Alexander Lukashenko has easily won reelection, according to official preliminary results released Monday, but the outcome has been widely disputed amid opposition accusations of vote-rigging.

The news, though expected, sparked protests late Sunday. Police violently dispersed the demonstrations with tear gas and water cannons. The opposition vowed to continue protesting the official results, while Lukashenko promised a “proper response.”

“We won’t allow the country to be torn apart,” he said, according to the state-run Belta news agency. He pledged that Belarus would not have a public uprising like the one that ousted Ukraine’s president in 2014.

In Minsk, images and video posted to social media Sunday night showed heavily armored riot police using stun grenades and rubber bullets to disperse demonstrators after a Central Election Commission official told state television that initial results showed Lukashenko claiming more than 80 percent of the vote.

His main rival, Svetlana Tikhanovskaya, received about 10 percent, according to further preliminary results released Monday. She drew crowds estimated at more than 60,000 at recent campaign events, thought to be the largest political rallies in the country since the dissolution of the Soviet Union.

Final results are expected Friday, the election commission said.

In a news conference Monday, Tikhanovskaya said that she will not flee the country and that she considers herself the true winner based on reports that her campaign received from polling stations. Maria Kolesnikova, her campaign chief, said the opposition is prepared for “long-term” protests.

Tikhanovskaya’s campaign said Monday night that after she went to the election commission building to demand a recount, she “vanished” and has not answered her phone. The commission denied that she has been detained in the building.

Election monitors pointed to the high turnout, especially in the five days of early voting, as a possible sign of ballot stuffing. Lukashenko’s five previous elections were not deemed free and fair, either, and analysts expected the official result to be in his favor.

“I will believe my own eyes — the majority was for us,” Tikhanovskaya said Sunday.

Internet access was widely disrupted throughout Belarus on Sunday and Monday, but videos posted to Twitter and opposition Telegram channels showed a line of protesters chanting “Leave” at a mass of riot police. Several journalists were beaten by police.

In one video, a police prisoner van appeared to run into a demonstrator in Minsk. Human rights groups said Monday that the person later died of head wounds and that dozens were hospitalized.

Protests in Gomel and Vitebsk also turned violent, but in some smaller cities, rallies were peaceful, and authorities did not move to disperse them. The Ministry of Internal Affairs said Monday that about 3,000 people were detained for participating in the protests Sunday night, but it denied that there were any casualties.

Sergey Livshits, 60, attended the Minsk demonstrations Sunday night with his wife. He said that being surrounded by people wearing white ribbons around their wrists, a sign of support for the opposition, “felt euphoric, as if we’d won.” The crowd around him was peaceful, he said, but throngs of people would start running at the sound of authorities firing rubber bullets and stun grenades.

“In the past, it was clear to many that [Lukashenko] was illegitimate, but now the society, including his supporters, feel that he is illegitimate and that he seized power,” Livshits said. “I think protests will continue.”

Alexey, who also attended the rally in Minsk but spoke on the condition that his last name not be used out of fear of reprisal, said he and others tended to wounded protesters after they were hit by the stun grenades.

“Those were not surface scratches, but like wounds from a burning cigar and a lot deeper,” he said.

Lukashenko said Monday that the protests were orchestrated from abroad, accusing Britain, Poland and the Czech Republic of “controlling” demonstrators. He also blamed foreign interference for the Internet shut-off.

Lukashenko, 65, has been in power for 26 years and is often referred to as “Europe’s last dictator.” Now, however, as he looks to extend his rule with a sixth term, he faces his most significant wave of domestic discontent over a slumping economy and his handling of the coronavirus pandemic. Belarus, which has a population of about 9.5 million, has more than 68,000 confirmed cases of the virus.

Lukashenko initially played down the coronavirus as “psychosis,” refused to enforce restrictions such as closing nonessential businesses and canceling mass events, and later said that he had contracted the coronavirus but endured it “on his feet.” There has been speculation about his health because he has been spotted with a catheter in his arm this month.

Lukashenko will also have to face frayed relations with powerful longtime ally Russia after 33 men detained late last month in Minsk were accused of being Russian mercenaries sent to the country to destabilize it ahead of the election. A rift between the two countries began when Russia intensified its push last year to form a unified state with Belarus — and Lukashenko resisted.

Russian President Vladimir Putin was the second world leader to congratulate Lukashenko on his victory; Chinese President Xi Jinping was the first.

The European Union said in a statement that “election night was marred with disproportionate and unacceptable state violence against peaceful protesters.”

Washington expressed concern, as well. Secretary of State Mike Pompeo said in a statement: “The United States is deeply concerned about the conduct of the August 9 presidential election in Belarus, which was not free and fair. Severe restrictions on ballot access for candidates, prohibition of local independent observers at polling stations, intimidation tactics employed against opposition candidates, and the detentions of peaceful protesters and journalists marred the process.”

In the run-up to Sunday’s election, authorities detained Lukashenko’s two main opponents; a third was barred from running and lives in exile. But Tikhanovskaya, the wife of jailed candidate Sergei Tikhanovsky, united the three strongest opposition camps to fight Lukashenko in a campaign fronted by three women.

Anastasia Shpakovskaya in Minsk contributed to this report.