Demonstrators take part in a protest against a partial coronavirus lockdown and against the Dutch government policy on Coolsingel street on November 19, 2021, in the port city of Rotterdam.
CNN  — 

At least two people were wounded after police in the Dutch city of Rotterdam fired warning shots during a protest over Covid-19 measures on Friday, the first of a handful of anti-lockdown protests planned across Europe this weekend.

Rotterdam Police said the demonstration on Coolsingel, one of the main streets in the center of the city, “resulted in riots.” They said numerous fires were started, fireworks were let off and officers were forced to use warning shots to disperse crowds.

“We fired warning shots and there were also direct shots fired because the situation was life-threatening,” police spokesperson Patricia Wessels told Reuters.

“We know that at least two people were wounded, probably as a result of the warning shots, but we need to investigate the exact causes further,” she said.

The unrest in Rotterdam on Friday involved several hundred protesters, the torching of cars and police vehicles being damaged.

The protests were organized after the Netherlands reimposed some lockdown measures last weekend for an initial three weeks, in an effort to slow a wave of coronavirus cases. Daily infections are at their highest levels since the start of the pandemic, as the country struggles to beat back a wave of transmission that has swept central Europe.

Protesters voiced their opposition to “corona passes,” which show a person’s vaccination status and are required to enter a number of public venues. The pass is also available to people who have not been vaccinated, but have proof of a negative test.

But they were condemned by Rotterdam’s mayor, Ahmed Aboutaleb, who called the event “an orgy of violence.”

“Police were forced to draw their weapons and even fire direct shots,” he said at a press conference on Saturday, Reuters reported. It was “an orgy of violence, I can’t think of another way to describe it,” he added.

The Rotterdam event is one of a number of anti-lockdown demonstrations planned for the weekend, with police in Vienna, Copenhagen and Budapest braced for protests. The Dutch capital Amsterdam is also expecting protests on Saturday afternoon.

Rotterdam police shut down public transportation and ordered people to go home on Friday as protests escalated.

Video posted on social media appeared to show burnt-out police cars and rioters throwing fireworks and rocks at police during the demonstration in Rotterdam on Friday.

In a statement on Twitter Saturday, Rotterdam police said at least seven people were injured. They did not disclose the severity or nature of the injuries but noted that police officers had also been injured.

At least 20 arrests were made following the unrest, according to police.

The police statement said they used a “maximum deployment of the police necessary to restore public order,” and urged people to stay away from Coolsignel.

Police issued an emergency ordinance in Rotterdam, shutting down public transportation and ordering people to go home. Water cannons were deployed and police on horseback carried out charges to disperse the crowds, police said.

The authorities also called on bystanders and people who recorded images of the riots to send the footage to police for further investigation.