The crackdown had the clear approval of President Alexander Lukashenko, who advocates rapid integration with Russia, and who said after last Friday's protest that he intends to ban all demonstrations.
The protest was timed to coincide with the 10th anniversary of the Chernobyl nuclear accident, which inflicted huge economic damage on Belarus and left it ill-prepared for independence when the Soviet Union collapsed in 1991. However, the rally quickly turned into one of the largest anti- government demonstrations of Mr Lukashenko's two-year-old presidency, with up to 50,000 people on the streets of the capital, Minsk.
Police dispersed the crowd with batons and several dozen people were reported injured. About 200 demonstrators were arrested, of whom roughly half were quickly released.
The main force behind the demonstrations was the Belarussian Popular Front (BPF). Its leader, Zenon Poznyak, told the crowd Mr Lukashenko's drive to unite Belarus with Russia represented "a quiet occupation of Belarus by Russia".
Mr Poznyak went into hiding after the protests and police later raided the BPF headquarters. A party spokesman said the tactics indicated Mr Lukashenko could be about to ban the BPF.