Dutch Prime Minister Mark Rutte has condemned riots across the country this weekend against a newly imposed nighttime curfew as "criminal violence."

Demonstrators attacked police with knives, threw rocks, set cars on fire and burned down a COVID-19 testing station to protest the curfew introduced on Saturday.

The police said hundreds of people had been detained after incidents that began on Saturday evening and lasted until the early hours of Monday.

"This has nothing to do with protest, this is criminal violence and we will treat it as such," Rutte told reporters outside his office in The Hague on Monday.

Schools and non-essential shops in the Netherlands have been shut since mid-December, following the closure of bars and restaurants two months earlier.

Rutte's government added a nighttime curfew running from 21:00 (20:00 GMT) to 4:30 as an additional lockdown measure from Saturday over fears that the British variant of the coronavirus may soon lead to an increase in cases.

According to the lockdown measure, anyone caught violating it faces a 95 euro ($115) fine.

Regional security councillors are reported to meet on Monday to discuss a response.

Dutch Police Union said there could be more protests ahead, as people grow increasingly frustrated with the country's months-long lockdown.

"We haven't seen so much violence in 40 years," union board member Koen Simmers said on television program Nieuwsuur.

There have been 13,540 deaths in the Netherlands from COVID-19 and 944,000 infections.

(With input from agencies)