Crowds of workers walked off the job on Friday at several factories in Belarus's capital Minsk in support of the opposition calling for leader Alexander Lukashenko to step down.
Hundreds of workers marched from the Minsk Automobile Plant (MAZ) and the Minsk Tractor Works (MTZ) after the opposition called for strikes against Lukashenko's disputed claim to have won re-election on Sunday.
Opposition candidate Svetlana Tikhanovskaya has claimed victory in the polls after raising up a nationwide protest movement. She left for Lithuania after allies said she came under official pressure.
The walkouts were highly unusual in a country where Lukashenko has retained a Soviet-style command economy and the tractor factory is seen as a national symbol.
Workers downed tools to condemn presidential elections where Lukashenko claimed a landslide victory against a popular opposition candidate and police violently cracked down on protesters.
The Belarusian Prime Minister Roman Golovchenko, appointed in June, came to visit the tractor plant but the striking workers left before he arrived.
On Friday afternoon they marched out of the factory into the city center, shouting "Long live Belarus" and "Leave!" directed at Lukashenko.
One of the strikers, a middle-aged man with a tattoo on his arm denoting support for the opposition, said that he wanted "to bring back Tikhanovskaya, she is our president, we voted for her."
On the streets outside the factory, members of the public waved flowers and honked horns in support of the strikers.
Tractor plant workers held banners responding to Lukashenko's disparaging comments on the protest movement.
"We're not sheep, we're not a herd, we're not little people" and "There's not 20 of us but 16,000," they said.
Lukashenko earlier Friday dismissed the walkouts at the tractor and auto plants, saying that "20 people decided to express their opinion, ditched work and went off."
He also warned that foreign competitors would benefit from strikes and suggested that workers were being paid to protest.
Belarus is regionally famous as a producer of tractors and they take part in a parade on its national independence day.
Workers at a major fertilizer plant, Grodno Azot, also protested in the city of Grodno, local media reported.
Belarus last saw such large-scale workers' protests and strikes ahead of the breakup of the Soviet Union in 1991. Lukashenko has been in power since 1994.