Tens of thousands of people marched through the streets of the Belarusian capital, Minsk, demanding the resignation of veteran President Alexander Lukasenko, despite officials threatening to use firearms against protesters.
Belarus, which has been closely allied with Russia, has been shaken by strikes and weekly street protests since the authorities announced that Lukasenko, who had ruled in an authoritarian manner since 1994, had secured reelection with an 80% vote on August 9.
The Interfax news agency increased the protesters to more than 30,000. Police have detained about 50 people and said mobile broadband signals were blocked in parts of the city.
The loud noise that sounds like a stunned grenade is said to be approaching the march. A senior police official said last week that the police would have the right to use firearms against protesters.
Security forces have detained more than 13,000 people since the elections, including all major opposition leaders who have not left the country and have been cracked down by independent media.
Opposition leader Svia Tlana Chicanusskaya, who fled to Lithuania, urged last week to face a national strike that would paralyze Belarus if Lukasenko does not quit by October 25.