The United Nations human rights chief Michelle Bachelet on Wednesday condemned the use of violence by Belarusian authorities to peaceful protests.

After President Alexander Lukashenko claimed a landslide victory in Sunday’s election, Bachelet said police were reported to have used excessive force, firing rubber bullets, using water cannons and throwing stun grenades, Reuters reports.

“Reports suggest that [approximately] 6,000 people have been detained in the last three days, including bystanders, as well as minors, suggesting a trend of massive arrests in clear violation of international human rights standards,” Bachelet said in a statement.

Even more disturbing are the reports of “ill-treatment during and after detention,” she said. The human rights chief called for the release of all those unlawfully detained and for investigations into abuses.