VIENNA, Dec 22 (Reuters) - Austria is introducing restrictions including a 10 p.m. closing time to slow the spread of the Omicron coronavirus variant after Christmas and prevent it being imported from Europe"s hardest-hit countries, a senior health official said on Wednesday. Austria began emerging from its fourth full coronavirus lockdown 10 days ago. While that three-week lockdown slashed daily COVID-19 infections, the country is bracing for another surge because of the extremely contagious Omicron variant, of which several hundred cases have been confirmed so far. Britain, the Netherlands, Denmark and Norway will be classified as risk areas because of the prevalence of the Omicron variant there, COVID-19 policy coordinator Katharina Reich told a news conference on new measures that she said were aimed at delaying the full onset of Omicron. New arrivals from those countries, some of which are among the winter sports hotspot"s biggest sources of tourists, will have to go into quarantine unless they have had a booster shot and can show a recent negative PCR test, Reich said. "We have always talked of a small breathing space. We must use this time we have gained (through the lockdown) well to learn more about Omicron on the one hand and to give hospitals more time to relieve pressure on intensive-care units on the other," she said. The 10 p.m. closing time will be imposed on the hospitality sector as of Dec. 27 and will remain in place on New Year"s Eve, she added, urging the public to celebrate that holiday only in small groups and with vaccinated people.