Thousands of demonstrators marched in the streets of Brussels on Sunday to protest against the government's latest strict measures to curb the spread of the coronavirus.

Twenty people were reported to have been arrested, according to the police, and four demonstrators and two police officers were injured in the clash.

Roughly 8,000 people took part in Sunday's demonstration, according to police estimate.

The protests were peaceful for most of the demonstration, until a small group of people clashed with police towards the end of the march near Brussels' European district of Schuman.

Police deployed water cannon and tear gas to dispel the rioters, causing some injuries and damage to police cars.

Belgian authorities on Friday decided to implement a slew of measures including further restrictions on indoor activities and reducing the age required to wear masks in indoor public spaces to six.

These measures entered into force on Dec. 4. The authorities will re-examine the epidemiological situation on Dec. 20.

So far, nine cases of the Omicron COVID-19 variant have been confirmed in Belgium, tweeted Belgian virologist Emmanuel Andre on Saturday who is in charge of the national reference laboratory for COVID-19.