The UN's special rapporteur on torture told Belarus on Tuesday that it must "stop torturing protesters" and bring to justice any police officers who have beaten them with impunity.
Nils Melzer and 14 other UN human rights experts said in a statement they had received reports of 450 documented cases of torture and ill-treatment of people deprived of their liberty in the mass protests and arrests following the disputed re-election of President Alexander Lukashenko.
"We are extremely alarmed at the hundreds of allegations of torture and other ill-treatment in police custody," they said.
The joint statement was signed, among others, by Anais Marin, special rapporteur on human rights in Belarus, and Clement Nyaletsossi Voule, special rapporteur on the promotion and protection of the right to freedom of expression.
The experts do not speak for the United Nations but report their findings to it.
They said torture "cannot be justified for any reason", nor could political instability be invoked to practice enforced disappearances.
"Authorities in Belarus must immediately put an end to all human rights violations and combat impunity," they said.
The experts said 6,700 people had been detained since the August 9 election — inlcuding journalists or passers-by "arbitrarily arrested and hastily sentenced."
"No person should be criminally charged for their peaceful participation in a demonstration," said the experts.
"We are also concerned that indiscriminate arrests continued over the weekend at a peaceful women's march in the capital, Minsk, on Saturday and at peaceful protests in many cities on Sunday," they added.
The experts said they would continue to monitor the situation and attempt to engage with the Belarus authorities.