Belarus, a former Soviet republic closely allied with Russia, has been rocked by mass street protests since President Lukashenko claimed victory in an August 9 election that his opponents say was rigged.
Belarusian police have detained hundreds of protesters in central Minsk, a witness said, as around 2,000 people marched through the city demanding that President Alexander Lukashenko step down.
Saturday's protesters, most of them women, briefly scuffled with police who then blocked their path and started picking people one by one out of the crowd, the witness said.
In one location, dozens of female protesters could be seen encircled by men in green uniforms and black balaclavas outside a shopping mall as they shouted, "Only cowards beat women!"
Among the detained was 73-year-old opposition activist Nina Baginskaya who has become an icon of the protest movement after scuffling with armed policemen last month.
One female protester was taken away in an ambulance after lying on the ground, apparently unconscious.
EU weighs sanctions
After the police stopped detaining people, the remaining protesters formed a chain along with one of the central streets of the capital and chanted "Long live Belarus!"
Lukashenko's crackdown on the protests has prompted the European Union to weigh fresh sanctions against his government.
Minsk reacted angrily on Saturday to reports that Svetlana Tikhanovskaya, the leading opposition candidate in last month's election could soon meet EU foreign ministers.
Russian Foreign Ministry spokesperson Maria Zakharova also criticised the EU for inviting Tikhanovskaya to the ministerial meeting as well as for considering sanctions against Minsk, saying Brussels was trying to "rock the boat" in Belarus.
Lukashenko, who has ruled Belarus for 26 years, says the protesters are being backed by foreign powers and has offered to end the standoff with constitutional reforms but he refuses to stand down.
Earlier this month he secured a $1.5 billion lifeline loan from Moscow.