THE HAGUE (NYTIMES, REUTERS, AFP) - Nations across Europe have been tightening restrictions to prevent the spread of the Omicron variant of the coronavirus, and on Saturday (Dec 18), the Netherlands became the first European country to announce a full lockdown to fight the variant.

Dutch leaders ordered the closure of all non-essential shops, bars, restaurants, gyms, outdoor sports, cultural venues and schools from Sunday (Dec 19) until mid-January.

"It's terrible," Dutch Prime Minister Mark Rutte acknowledged on Saturday during a televised news conference.

"This is terrible for everyone, especially on the eve of the holidays."

Mr Rutte said that a fifth Covid-19 wave was inevitable in the country because of the new highly contagious Omicron variant.

"We have to act now to prevent a worst-case scenario," he said.

"Without measures, we could be witnessing an uncontrollable situation at the start of January."

The Netherlands, normally a well-organised country, has struggled more than many other wealthy nations to control the spread of the coronavirus, and its booster campaign has also been progressing relatively slowly.

Dutch Health Minister Hugo de Jonge said efforts to mass-administer booster shots would be drastically increased.

"We need this to buy time in order to find out how sick the Omicron variant can make us," Mr de Jonge added.

Researchers are racing to determine whether the Omicron variant might have more or less virulence than earlier iterations of the virus.

Official measures against the coronavirus have not always fared well among the Dutch.

Anger over the country's partial lockdown and other restrictions set off unruly and sometimes violent protests last month and earlier this year in several cities.

Other European countries have also taken action as they detect the Omicron variant in an increasing number of case samples.

Austria announced tougher entry restrictions for travellers without booster shots.

In Denmark - one of the first countries in Europe to see a surge of the new variant - theatres, concert halls and amusement parks have been closed.

Ireland imposed an 8pm curfew on pubs and bars starting on Sunday (Dec 19), among other new restrictions.

All countries are looking towards Britain, which has so far been the hardest hit in the region, with a total of 37,101 confirmed Omicron cases on Sunday.

Britain reported 90,418 new coronavirus cases on Saturday - down from a record of just over 93,000 on Friday.

Cases were up 44.4 per cent over the seven days to Saturday, compared with the previous week.

British Health Minister Sajid Javid on Sunday declined to rule out the chance of further restrictions before Christmas.

"The situation... is very fast moving," Mr Javid said, adding that the government was taking seriously the "sobering" advice of its scientists, was watching the data on an "almost hourly basis", and would balance that against the broader impact of restrictions on things such as businesses and education.

Government advisers have said the Omicron cases currently reported in Britain could be only the tip of the iceberg.

Mr Javid said the government believed that around 60 per cent of new Covid-19 cases in England were now Omicron.

Germany late on Saturday announced that it would add Britain to its list of Covid-19 high-risk countries.

The change, which kicks in on Sunday, means arrivals from Britain will have to observe a two-week quarantine regardless of whether they are vaccinated.

Paris on Saturday said it would call off its New Year fireworks in an effort to rein in Covid-19 infections, after French Prime Minister Jean Castex on Friday likened the spread of Omicron in Europe to "lightning".

European Union chief Ursula von der Leyen has warned that the Omicron variant could be dominant in Europe by mid-January.