One worker in the capital, Minsk, told the Associated Press she was asked to sign a document with the vote totals left blank even before the election concluded.
Another who pointed out violations during vote-counting was sacked on the spot.
In the city of Vitebsk, a poll worker said he signed a document with falsified results in favour of Mr Lukashenko, and is wracked with guilt for betraying the trust of the voters.
In the three weeks since the election, hundreds of thousands of people have protested against what they say was a rigged outcome.
Demonstrations and strikes in the country have been met by a police crackdown including mass detentions, beatings and criminal charges against organisers.
The Associated Press interviewed election workers who said they saw ballot fraud or were pressured to falsify results in favour of Mr Lukashenko.
In addition, other evidence has been posted online showing falsifications and other irregularities.
To many in Belarus, where Mr Lukashenko has ruled with an iron fist since 1994 and has been accused of rigging previous elections, his victory last month seemed clearly implausible.
His main opponent, former English teacher Sviatlana Tsikhanouskaya, drew crowds of tens of thousands of people after she entered the race in place of her husband, Sergei, a popular opposition blogger who was jailed before the election.
She had managed to unite fractured opposition groups, channelling the growing frustration over the country’s weak economy and Mr Lukashenko’s swaggering dismissal of the coronavirus pandemic.
When the results were announced, however, the Central Election Commission said Mr Lukashenko won 4.6 million votes, or 80%, and Ms Tsikhanouskaya received only 588,000, or 10%.
The opposition was prepared for such an outcome – allegations of rigged elections have surfaced in every vote in Belarus since Lukashenko took power in 1994.
This time, it trained people to be independent monitors at polling stations, it encouraged poll workers to report violations, and set up a website where voters could submit photos of their marked ballots to compare with the official count.
Activists monitoring the election said in a report that they received complaints about violations, irregularities and incidents of some form of vote-rigging from at least 24% of the country’s 5,767 precincts.
The report said that they studied just under a quarter of the nation’s precincts and found that Ms Tsikhanouskaya received more than 471,000 votes in those areas alone.
Valeria Artikhovskaya, who worked at a polling station in Minsk, said she still does not know the official results of the vote at her precinct because they were never released.
Ms Artikhovskaya said she was asked to sign the final protocol – a document summing up the vote totals each precinct must display after counting the ballots – before voting even ended, with the totals left blank.
She refused, and once the count started, she noticed other poll workers putting ballots for different candidates into a stack for Mr Lukashenko.
“I said I wouldn’t sign the protocol because it’s a crime, it’s fraud. (I said,) ‘Allow me to recount these ballots,’ and they refused. I didn’t sign the protocol and left the precinct,” the 30-year-old told the AP on Friday.
“My conscience is dearer to me.”
Vadim Korzykov, who worked at another Minsk polling station, told AP he did not even get to the signing stage – a senior poll worker dismissed him after he pointed out violations during the count.
The 20-year-old student said his colleagues told him later that the number of votes for Ms Tsikhanouskaya at the precinct was five times higher than what Mr Lukashenko received there.
“It was a travesty of justice. There is no other name I can call it,” Mr Korzykov said in a phone interview.
Andrei Gnidenko, who worked at a poll in Vitebsk, a small city in north-eastern Belarus, said he gave in to the pressure and signed a document with falsified results.
According to the final protocol from the station, a photo of which Mr Gnidenko showed AP, Ms Tsikhanouskaya got a total of 156 votes, while Mr Lukashenko received 488. But Mr Gnidenko says he and other workers counted more than 250 ballots for Ms Tsikhanouskaya.
When the time came to sign the protocol late at night, everyone was exhausted, and a crowd of residents had gathered outside the polling station, demanding to see the results.
Mr Gnidenko felt sorry for everyone and decided to get it over with, a decision he now regrets.
“For the next few days, we were all very severely depressed,” the 29-year-old said.
“I decided that since I betrayed the Belarusian people, since I took part in this rigging and put my signature on it, it was my duty to honestly tell it (to the public).”
An audio recording from another polling station in Vitebsk was posted on YouTube in which poll workers are heard being told by an official to falsify the results in favour of Mr Lukashenko.
The official suggests that poll workers “swap the numbers” for Mr Lukashenko and Ms Tsikhanouskaya.
“I’m prepared to agree that a lot of people voted for Tsikhanouskaya … but we have other goals and other problems we need to solve,” the official says. After some back and forth, poll workers swap the results.
Some of the workers later confirmed to Belarusian media the authenticity of the recording, which has received more than 450,000 hits on YouTube.
Alexander Khomich, a spokesman for the activist group Honest People that monitored the election, said Ms Tsikhanouskaya got significantly more votes and Mr Lukashenko got significantly fewer votes.
“Given the manner in which the vote has been rigged, I can vouch that no-one – not us, not the Central Election Commission – knows the real result of the election,” Mr Khomich told the AP.
The Central Election Commission has refused all the candidates’ requests for a recount, and Mr Lukashenko bristled at demands to rerun the vote.
The results were not recognised by the four candidates on the ballot with Mr Lukashenko.
Both the US and the European Union have called the election neither free nor fair, and EU foreign ministers are preparing sanctions against senior Belarus officials suspected of election fraud and the subsequent crackdown on protesters.
The Belarus supreme court last week refused to overturn the vote, saying it could not rule after election authorities declared it valid.
