Police officers across Belarus have begun arresting protesters, having already detained about 80-100 people in Grodno and about 40 - in Brest.
Police also arrested dozens in Minsk. No precise number of detainees is available.
Earlier today, security forces used teargas to dismantle the protesters in Lida, Belarus.
Today, the ultimatum to Belarusian President Alexander Lukashenko by opposition leader Svetlana Tikhanovskaya expires.
Protests in Belarus began after the presidential election results were declared.
Citizens state the August 9 elections were held in violation of the rules.
They demand the resignation of Alexander Lukashenko.