NHS staff are “stretched to their limit” as hospitals try to cope with more than 2,300 Covid patients, one of Wales’ most senior doctors has warned.
The deputy chief medical officer said critical care units were “operating far beyond their normal capacity”.
Dr Chris Jones told a briefing there were more than 100 deaths with Covid-19 reported over the weekend.
It comes as the new variant of the virus as been found “all over Wales” – with at least 600 cases.
“Unless we can regain some control of the spread of coronavirus, I am sorry to say we will see more deaths,” said Dr Jones.
Figures from the Office for National Statistics suggest 28% of sample swabs taken in the second week of December were the new variant of the virus.
But Dr Jones said public health colleagues “feel this new strain could be causing up to 60%” of Covid infections in Wales.
“This new variant looks very likely to be the significant driver of the huge growth in cases we’ve seen in Wales in recent weeks.”
Public Health Wales said there had been 2,563 further cases of coronavirus recorded in Wales on Sunday, with 10 deaths with Covid-19 confirmed.
It means 3,125 have now died with the virus.
Dr Jones added: “It is clear that the public health situation has been a cause for concern for some weeks.
“But the issue of the new virus variant is very, very recent indeed.
“We only need to know about such variants when they take off, and that only became clear at the end of last week.”
Addressing the briefing, the First Minister Mark Drakeford defended imposing stricter restrictions on Wales at the weekend.
Mr Drakeford said new knowledge had emerged, which required action.
Wales was placed in the new alert level four on Saturday, effectively locking down Wales over Christmas.
“I don’t think it would be a fair thing to say at all that we have been slow to act, we have acted in response to the views of clinicians in response to the rising cases,” said the first minister.
“What was different this weekend was that we had a new explanation for why we are seeing the rate of increase here in Wales – this new variant with its transmissibility, the speed with which it spreads.
“And that’s why we had to bring forward our plans for a tier four set of restrictions across Wales.”
He also said talks were being held with trade unions in a bid to ensure those working on Christmas Day will still get to see their family.
If follows a letter from Rhondda Senedd member Leanne Wood urging key workers to be allowed to meet loved ones on the following day.
Under the new restrictions, you are only able to travel to meet one other household – and a single person household – on Christmas Day anywhere in Wales.
“Of course there will be people who will be working on Christmas Day to allow the rest of us to be able to have that day to be with a small number of other members of our family,” said Mr Drakeford.
“We are discussing with the TUC and others whether it would be possible to offer those people who are working on that day any compensatory arrangements.”
Following what was the final coronavirus briefing from the Welsh Government before Christmas, officials confirmed the first minister has developed a cold, but had a precautionary Covid-19 test, which was negative for the virus.