Police said about 2,500 people gathered in central Minsk to protest against the government's insufficient efforts to reduce the consequences of the devastating disaster at the Chernobyl nuclear power plant in 1986, which killed and affected nine million people, according to UN estimates.
The protesters are also opposed to the authorities' plans to build a nuclear power plant and to allocate polluted areas for farmland.
Opposition supporters gathered near the building of the Academy of Sciences and moved toward a church built in memory of the Chernobyl victims, where they laid flowers and held a minute of silence.
The opposition holds the demonstration every year. The most violent meeting took place in 1996, when protesters turned over cars and beat up journalists.