The United Nations human rights office has criticized Malaysia's crackdown on demonstrators calling for electoral reform.

Rupert Colville, spokesman for the U.N. High Commissioner for Human Rights, said Tuesday the U.N. is “very concerned” about Saturday's use of tear gas and water cannons on tens of thousands of people rallying in Kuala Lumpur. Malaysian authorities said the protest was illegal and arrested more than 100 organizers before the rally began. As police officers broke up the gathering, they detained hundreds of people for several hours.

The human rights office quoted police as saying 1,600 detained demonstrators have been released. But Colville says concerns remain about retaliation against those detained as as well as those arrested in the hours before the demonstration.

Colville says his office is disappointed to see the apparent use of excessive force on the crowds, as well as the targeting of individuals championing the rights of Malaysian citizens to express themselves and assemble peacefully.

The protesters were calling for voting reform ahead of next year's general elections. The government has defended the actions of the police, saying they acted to keep peace and security.