Masked men in uniforms violently confronted a protest in Minsk on Saturday attended by thousands of women calling for the removal of authoritarian President Alexander Lukashenko.
In one instance, a young woman suffered a face laceration after she pulled a stocking mask off of an officer and he struck back by beating her.
Viasna, a human rights organization on the ground in Belarus, said at least 70 people were detained in the capital city. A reporter saw several female protesters being forced into vans.
There were protests in other cities as well.
The anti-Lukashenko protests that have swept across Belarus are banned by the government, although rallies by his supporters are allowed to go ahead.
A small crowd of supporters gathered at Victory Square on Saturday, while the much larger rally of Lukashenko's opponents met at Freedom Square. A main theme of the latter protest was the imprisonment of opposition politician Maria Kalesnikava.
"Give us back our Masha," the women chanted.
Kalesnikava, 38, is a member of the praesidium of a coordination council seeking a peaceful transition of power in Belarus.
Her supporters claim she was violently detained by unidentified masked men in central Minsk earlier this week, and now faces a charge of attempting to overthrow Lukashenko.
She was moved to a different prison outside Minsk on Saturday. The opposition wrote on Twitter that they had not been told the reason for the move.
Saturdays in Minsk have been marked by women's protests in recent weeks. A much larger rally is set for Sunday in which tens of thousands of people are expected to turn out.
Solution through dialogue
German Foreign Minister Heiko Maas said that the many peaceful protesters "prove every day that a solution through dialogue is still possible."
"To show so much attitude, courage and dignity in the face of massive repression - that deserves the utmost respect," Maas said, in comments published by the Funke Media Group on Sunday.
"Now it is important that we do not leave the people in Belarus alone," he said.
There have been protests every day in Belarus since a presidential election more than a month ago. The opposition, as well as European Union officials, allege that Lukashenko rigged the vote to maintain his grip on power.
Kalesnikava is a close ally of Svetlana Tikhanovskaya, who came second in the August 9 election, according to the disputed official result. Tikhanovskaya's supporters say that she won the election.
Tikhanovskaya, who is in exile in Lithuania, condemned the crackdown against the women and delivered a message to the officers via Twitter: "You have the chance to switch to the side of the people and no longer carry out criminal orders."
During the protest, Lukashenko met with his National Security Council.
According to the state news agency Belta, in light of the NATO military exercises happening in neighbouring Lithuania, he said that when the drills were over, the Belarusian army should "respond appropriately."
Most recently, Belarusian armed forces had been relocated to the country's western border. In addition, Lukashenko had part of the army placed on "full combat readiness."