MOSCOW — President Vladimir Putin's United Russia party is expected to maintain its grip over the State Duma, or lower house, exit polls in the country's parliamentary elections showed Sunday, amid complaints by opposition parties and independent observers of widespread fraud.

Early results released after polls closed in the three-day vote also put United Russia ahead of the Communist Party and other rivals. The polling agency Insomar predicted United Russia would win with 45 percent of the vote.

Opposition parties and observers reported ballot stuffing and other tampering during the three days.

"The elections are being stolen from us," said Mikhail Lobanov, 38, a university lecturer running with the Communist Party in southwest Moscow.

Ella Pamfilova, chief of the Central Elections Commission, said the number of violations was lower than in previous elections. She said 12 cases of ballot stuffing had been confirmed. Mikhail Davydov, the head of the Interior Ministry's main department for the protection of public order, said there were no violations significant enough to affect the elections.

The vote was held amid a sweeping, months-long crackdown on the opposition.

A three-day parliamentary election in Russia came to a close on Sept. 19. (Reuters)

Opposition leader Alexei Navalny is in jail. His electoral network was declared an extremist organization in June and effectively banned. Its leaders, other opposition figures, human rights activists, human rights lawyers and independent journalists have been arrested or fled the country. Dozens of opposition candidates were barred from running or withdrew under threat of arrest.

Results were expected to be announced Monday.

Navalny’s network on Sunday urged Russians to turn out and vote against United Russia.

“Today is the day your vote really matters,” the network said in a message in his name posted to his Instagram account. “Because today is the day that each of us can be especially efficient in convincing the doubters.”

The network urged Russians to follow voting recommendations published on its “Smart Voting” list, a tool to direct votes away from Putin’s party.

Multiple videos surfaced that appeared to show ballot stuffing and other tampering. The nonpartisan election monitor Golos on Sunday reported nearly 3,800 possible violations, including ballot stuffing and possible vote buying.

Golos also criticized the decision to hold the voting over three days, ostensibly a pandemic measure, saying it left ballots vulnerable to interference over two nights. The election monitor reported sealed plastic envelopes for vote storage being tampered with and containers with ballots being stored in rooms with no video surveillance.

Videos of units for overnight storage of votes showed that seals on rear doors could easily be peeled off and replaced.

Golos also reported intimidation of observers by election officials or thugs.

Communist Party leader Gennady Zyuganov on Saturday described the alleged tampering as “criminal” and called on police to investigate.

“There are huge violations of the law by the authorities,” he said. “In fact, the entire system of the election commission headed by Ella Pamfilova and Nikolai Bulayev is covering up these violations.

“With all of this, I do not rule out the possibility of mass protests. I am convinced that people will not tolerate the brazen substitution of their choice.”

United Russia has won all four Duma elections since 2003, two with a supermajority: 300 of the 450 seats. It held 334 seats in the previous Duma, giving the Kremlin a compliant body that was criticized for rushing through repressive laws.

Lobanov, the Communist Party candidate in southwest Moscow, faced an uphill battle against United Russia’s high-profile candidate, said state TV host Yevgeny Popov.

“We knew that the assurances of clean elections in Moscow were a bluff, so we prepared an army of observers in advance,” he tweeted. “But our observers are not enough.” He said he had seen many cases of ballot stuffing.

“It is important for us to catch every fraudster by the hand, to record every violation on video, to prevent them from stealing our elections.”

In Bryansk, southwest of Moscow, official video taken at a polling station appeared to show people having difficulty stuffing wads of votes into the ballot box. At least two videos taken in Kemerovo in southwest Siberia appeared to show a hand emerging from behind a curtain to stuff multiple votes into a ballot box. They were reported by the opposition Yabloko party.

A video allegedly taken in Vladivostok in Russia’s Far East appeared to show a person marking multiple ballot papers.

At a polling station in Nizhny Novgorod, east of Moscow, an observer reported Saturday that 200 more ballots were cast than there were total voters. In Samara, east of Moscow, Yabloko observers said 1,680 people were reported as voting at a polling station over five hours, yet video recorded just a slow dribble of voters during that time.

In St. Petersburg, Yabloko candidate Nikita Sorokin was arrested after he reported that several hundred blank ballots had gone missing. Supporters said he was beaten by police.

The elections also saw a further whittling back of Internet freedom in Russia as access to the Navaly network’s Smart Voting list was blocked. Russia’s Internet censor, Roskomnadzor, banned the list based on the court ban on the network.

The Smart Voting app was removed from Apple and Google stores in Russia on Friday as voting began. Access to Smart Voting videos, with Google documents appended directing opposition voters to the candidate in each seat most likely to defeat Putin’s United Russia, was later blocked on YouTube.

Telegram temporarily blocked the network’s chat bots, which the network was using to distribute its recommendations.

“We consider this practice to be legitimate and call on Telegram users to respect it,” Telegram founder Pavel Durov said in a statement. “Hopefully everyone who wishes to obtain additional information about the candidates was able to do so before the elections.”

Apple and Google did not respond to requests for comment after the apps were removed Friday.

A Google document with the Smart Voting recommendations was also blocked, but Navalny’s team and others created new Google documents with the voting recommendations and circulated them on social media.

Navalny aide Leonid Volkov said the media giants had bent to pressure from authorities to block Smart Voting and warned that the action would have far-reaching consequences for Russia. “They’ve opened Pandora’s box. This will end badly,” Volkov said.

Michael McFaul, a former U.S. ambassador to Russia, criticized the tech companies for blocking the Navalny information while allowing pro-Kremlin materials.

“If social media companies truly want to be impartial in elections, then they have to treat all candidates equally,” he tweeted. “In Russia, for instance, you can’t censor the small d democrats unless you also censor the autocrats.

“Maybe social media companies cannot defy autocrats,” he added. “But more minimally, they can stop helping them.”

Political analyst Andrei Kolesnikov of the Carnegie Moscow Center said Russian authorities want to convince opponents it’s useless to resist.

“Just like any autocratic regime, they want total support,” he said. “They want big figures. It’s not enough for them to have 40 percent or 30 like in a democratic system. They see it as weakness if they do not have high figures. . . .

“They want to demonstrate that ‘We are still the majority. Don’t go to the streets because it’s senseless. You will be suppressed,’ ” he said.

Russia’s Central Elections Commission on Saturday reported cyberattacks from abroad targeting its website and system on Friday.

Golos co-founder Grigory Melkonyants said United Russia was treated to five times more airtime on state television before the elections than all the other parties put together. He said more than 9 million people were ineligible to run, for example, because of past offenses such as protesting.

The Organization for Security and Cooperation in Europe did not send observers because Russian authorities imposed restrictions on their activities.