Belarusian President Alexander Lukashenko has been heckled by workers on a visit to a factory as anger mounts over his disputed re-election.
Workers chanted “leave” and booed the long-time leader of the ex-Soviet state as he insisted he would not allow a new vote after allegations of ballot fraud.
Strike action spread to state TV, with staff walking out on Monday.
Opposition candidate Svetlana Tikhanovskaya has suggested she could act as an interim leader.
Police violence towards opposition supporters, as well as the alleged poll-rigging in the 9 August vote, fuelled a big protest rally in the capital Minsk on Sunday.
Mr Lukashenko has led Belarus since 1994, maintaining close relations with neighbouring Russia, on which Belarus heavily relies for energy supplies.
How great is the pressure on Lukashenko?
According to local, independent news site Tut.by, Sunday’s opposition rally in Minsk was “the largest in the history of independent Belarus”.
A wave of anger has been rising since the Central Election Commission said Mr Lukashenko had won 80.1% of the vote and Ms Tikhanovskaya – 10.12%.
Some 6,700 people were arrested in the wake of the election, and many have spoken of torture at the hands of the security services.
On a visit to the Minsk tractor plant on Monday, Mr Lukashenko sought to defend his disputed victory, telling workers: “We held the election. Until you kill me, there will be no other election.”
But as he spoke, workers booed him and chanted “leave”.
Last week, workers at state-run factories walked out in solidarity with the protesters, and more strikes are planned for this week, increasing the pressure on Mr Lukashenko, says the BBC’s Kyiv correspondent, Jonah Fisher.
A state TV broadcast on Monday morning showed empty news desks. Staff walked out in protest against censorship and the election results.
Ms Tikhanovskaya, who left for Lithuania after publicly denouncing the results, insists that where votes were properly counted, she won support ranging from 60% to 70%.
In a video message released on Monday, she said she was ready to become a “national leader” in order to restore calm and normality, freeing political prisoners and preparing for new elections.
How did Sunday’s rallies play out?
Rival rallies were held in the capital, with the opposition event appearing to attract much higher numbers.
An official report said 65,000 people had attended the presidential rally but unofficial estimates were as low as 10,000. Unofficial estimates for the opposition gathering ranged between 100,000 and 220,000.
There were reports of state sector workers being forced to attend Mr Lukashenko’s rally or face the threat of losing their jobs.
As the president spoke, the anti-Lukashenko protesters gathered for a peaceful rally near the Stela Minsk Hero City World War Two memorial in the city centre.
Supporters also turned out in other cities, following a call for weekend rallies from Ms Tikhanovskaya.
A number of officials, as well as current and former police officers, have resigned.
The Belarusian ambassador to Slovakia, Igor Leshchenya, declared his solidarity with the protesters but told the BBC the government did not seem ready to hear them.
What’s happening internationally?
EU leaders are to hold an emergency video summit on the Belarusian crisis on Wednesday. EU foreign ministers agreed last week to prepare new sanctions against Belarusian officials responsible for “violence, repression and the falsification of election results”.
The UK said on Monday it did not accept the results of the “fraudulent” election.
“The world has watched with horror at the violence used by the Belarusian authorities to suppress the peaceful protests that followed this fraudulent presidential election,” said Foreign Secretary Dominic Raab in a statement. “The UK does not accept the results.”
The US has condemned the election as “not free and fair”.
More about the protests in Belarus
President Lukashenko has sought Russian help, saying President Vladimir Putin has promised to provide comprehensive assistance in the event of any external military threat.
In a conversation on Sunday, the two men discussed “the situation in Belarus, taking into consideration the pressure the republic was being put under from outside”, the Kremlin said.