Lukashenko's opponents defied a police ban to stage a massive anti-government rally in Minsk on the strongman's birthday. Some 125 people were arrested after trying to join the event in Belarusian capital.
Opposition sources estimated some 100,000 protesters marched through the Belarusian capital. Many of the participants carried placards mocking Lukashenko, who turned 66 on Sunday.
Participants also chanted "Happy birthday, you rat," and called for Lukashenko's arrest.
Russia's Vladimir Putin, however, congratulated Lukashenko in a phone call, in what could be seen as a sign of support for the Belarusian leader. The Kremlin said the two presidents agreed on Lukashenko visiting Moscow "in the coming weeks."
Videos shared on a Telegram-based news channel showed security forces as they began arresting people and pulling them into police vehicles as nearby protesters reportedly yelled, "shame!"
Police had cordoned off the central Independence Square in an attempt to keep demonstrators away from nearby government buildings.
DW's Nick Connolly shared images from the protest.
On the last two Sundays, hundreds of thousands of people took to the streets in Belarus to protest against Lukashenko, who protesters call "Europe's last dictator."
The police response to the protests has fluctuated between extremely heavy-handed to mild since the rallies started earlier this month. This Sunday's arrests and others earlier this week could indicate that the government's tolerance toward the demonstrations is dwindling.