Welsh football fans will be locked out of stadiums from Boxing Day onwards.
The restrictions affecting all levels of sport in Wales start on December 26 with no end date given. It comes as coronavirus cases continue to rise, with the Omicron variant now prevalent.
In a statement, the Welsh Government said: "The latest figures showed a further steep rise in the number of confirmed cases of the fast-moving variant."
The first football game to be affected is Wrexham's National League clash with Solihull Moors.
The Dragons, who were taken over by A-list duo Ryan Reynolds and Rob McElhenney earlier this year, released a statement.
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It said: "We are disappointed that fans will be unable to attend our scheduled Boxing Day fixture at the Racecourse Ground, but we understand why the decision has been made.
"For any game that is played behind closed doors while these restrictions are in place, the Club will refund all moneys paid and will share more details regarding this in due course. This will apply to both season ticket holders and those who have bought tickets for the specific match(es).
"Please retain any tickets already purchased and continue to collect tickets in the normal way. We will communicate all further information, including the refund process in due course."
Cardiff City's next scheduled home game is not until Sunday, January 9 when they host fellow Championship side Preston North End in a third round FA Cup tie.
Their Boxing Day meeting with Coventry has already been called off due to a Covid outbreak within the Bluebirds' camp.
Swansea City's next scheduled home game is on December 29 when they welcome Luton Town. That game will now be played behind closed doors.
League Two outfit Newport County are not due to play at Rodney Parade again until January 8, after their Boxing Day visit of Forest Green Rovers was postponed due to a Covid outbreak.
Welsh economy minister Vaughan Gething said: "Sporting events over the Christmas period are one of the big highlights of the year. Unfortunately, the new omicron variant is a significant development in the pandemic and could cause a large number of infections.
"We need to do everything we can to protect people's health and control the spread of this awful virus.
"Throughout the pandemic we have followed scientific and public health advice to keep people safe. The advice is clear - we need to act now in response to the threat of Omicron. We are giving people as much notice of these decisions as we can.
"Crowds will come back as soon as possible. We want everyone to be here to enjoy their favourite sports."
The new rules will apply to all levels of sport held within Wales, including semi-professional and grassroots.
In horse racing, the Welsh Grand National which is being held at Chepstow on December 27 will also now be staged without spectators.