Update: The protester who was previously reported to have been killed has survived, Reuters reported.
A protester was killed and dozens wounded when police in Belarus used stun grenades, rubber bullets and tear gas to disperse demonstrators disputing election results, a prominent rights group said on Monday.
The Viasna Human Rights Center said the young male protester suffered a traumatic head injury when he was hit by a police vehicle and medics were unable to save him.
Viasna representative Sergey Sys told AFP that more than 300 people had been arrested on Sunday, including more than 150 in the capital Minsk.
"Dozens of people were wounded as a result of clashes with law enforcement agencies. Ten of them were taken to hospitals," he said.
Police in Belarus detained some 3,000 people for taking part in the unauthorized gatherings, the interior ministry said, accusing some protesters of sparking clashes with police.
The ministry said in a statement that 1,000 of the detentions were in the capital Minsk and the rest in other parts of the country.
It said protesters in Minsk had lit flares, erected barricades and thrown objects at police. Fifty civilians and 39 police officers were injured in clashes in the capital, it said, denying there were any deaths.
Long-serving Belarusian leader Alexander Lukashenko won a sixth term in Sunday's election with 80.23% of the vote, the central electoral commission said Monday, a result the opposition says was rigged. His main challenger, Svetlana Tikhanovskaya, won 9.9%, central electoral commission chief Lidia Yermoshina said.
Tikhanovskaya rejected the results and demanded authorities transfer power to the opposition.
"Yesterday the voters made their choice but the authorities did not hear us, they have broken with the people," she told a news conference Monday.
She also denounced authorities for the crackdown, saying police had used "disproportionate measures" against protesters and called disruptions to the internet "a crime."