Wales will go into full lockdown from December 28, First Minister Mark Drakeford has announced.
The Welsh Labour leader said a “sustained rise in coronavirus” meant that the country would have to move into its highest level of restrictions.
Mr Drakeford also said the planned five days of relaxed measures would remain in place following talks between the four UK nations.
Some measures will come into force on Christmas Eve with all non-essential retail, including close contact services and all leisure and fitness centres forced to close from the end of the day.
All hospitality premises will be forced to close from 6pm on Christmas Day.
But tighter restrictions for household mixing, staying-at-home, holiday accommodation and travel will only apply from December 28, with the planned easing of Covid restrictions over Christmas remaining in place between December 23 and 27.
Mr Drakeford told the Welsh Government press briefing on Wednesday: “Many of you will have seen the warnings from senior clinicians about the huge impact coronavirus is having on the whole of our health service.
“The situation we are facing is extremely serious. We must move to alert level four and tighten the restrictions to control the spread of coronavirus and save lives.
“This new set of higher-level restrictions will apply to the whole of Wales.
“This means all non-essential retail, including close contact services and all leisure and fitness centres will close at the end of trading on Christmas Eve.
“All hospitality premises will close from 6pm on Christmas Day.
“And on December 28, at the end of the five day Christmas period, tighter restrictions for household mixing, staying-at-home, holiday accommodation and travel will apply.”
Mr Drakeford said joint UK-wide advice about Christmas would be published later but said that a “shorter Christmas is a safer Christmas”.
“Yesterday, I met the first ministers of Scotland and Northern Ireland and Michael Gove from the UK Government to discuss the common arrangements for the five-day Christmas period,” he said.
“We had a further meeting this morning. In the few short weeks since we made this decision, the situation has changed drastically as coronavirus has gripped the UK country once again.
“Later today, we will publish joint advice across the UK, explaining that a smaller Christmas is a safer Christmas.
“That a shorter Christmas is a safer Christmas.
“Here in Wales, the position is that only two households should come together to form an exclusive Christmas bubble during the five-day period.
“The fewer people we mix with in our homes, the less chance we have of catching or spreading the virus.
“None of us wants to be ill this Christmas. And we don’t want to give coronavirus to our close family or friends.
“The chief medical officer for Wales has provided special advice for people who were previously shielding about mixing over Christmas.”