A demonstration with several hundred people in the Netherlands' second-largest city turned violent Friday evening with rioters setting fire to cars and clashing with riot police.
Police said they fired water cannons and warning shots to disperse rioters, and at least seven people were wounded. At least 20 people have been arrested so far.
"We fired warning shots and there were also direct shots fired because the situation was life-threatening," police spokesperson Patricia Wessels told Reuters news agency.
Police have not commented on the state of those injured, but said their officers were also wounded.
Dutch broadcaster NOS said at least one police car was set on fire and others were damaged. Police officers and firefighters were also pelted with objects.
Images posted on social media showed cars on fire, fireworks being ignited, and debris and trash bins on fire in the street and rioters throwing stones and fireworks at police.
Authorities shut down public transportation in the city, closed the main train station and ordered people to go home.
How have authorities reacted?
Local political party Leefbar Rotterdam condemned the violence in a tweet, saying the "center of our beautiful city has this evening transformed into a war zone."
"Rotterdam is a city where you can disagree with things that happen but violence is never, never, the solution," the tweet read.
Rotterdam's mayor Ahmed Aboutaleb said the riots were an "orgy of violence." He told reporters that violence forced officers to "draw a police weapon in the end to defend themselves."
Why were people demonstrating?
A demonstration had been called by several organizations in opposition to a government plan to restrict access to indoor venues to people who have a "corona pass" proving they are vaccinated or have recovered from Covid-19.
Last week, the Netherlands partially reimposed lockdown measures to slow a resurgence of the virus, with daily infection numbers at some of their highest levels since the beginning of the pandemic.
Last January, when a curfew was imposed in the Netherlands, riots in several cities caused millions of euros in damage.