Coronavirus: Irish cabinet agrees raft of tighter restrictions
The Irish government has announced a raft of measures to fight the coronavirus including school closures.
Non-essential construction will also be shut down and air passengers must have negative Covid-19 PCR tests 72 hours before flying into the state.
PCR tests are regarded as the "gold standard" of testing.
The travel restriction will apply to passengers from Britain and South Africa before an anticipated extension to all visitors.
The Taoiseach (Irish PM) has told a news conference that public compliance with the measures will reflect on how many people may die.
Mícheál Martin said he expected people to "face the coming month with steely determination and resolve."
The Tánaiste (Irish deputy prime minister) has described the republic's covid situation as "bad and getting worse."
Leo Varadkar said the republic is "facing into what's going to be a really dark January."
But he said Ireland is much better placed than in March and that, even in these dark moments, there is the hope of the vaccine.
He told a news conference he expected the numbers getting the vaccine to be ramped up in the coming weeks and months.
"January is the month we all stay in," he added.
Schools for most pupils will close from next Monday, but final year secondary students doing the Leaving certificate exam - the Irish equivalent of A levels - will continue to attend three days a week.
Non-essential construction will stop on Friday at 18:00 local time on 18 January.
But building work will be allowed to continue in such projects as social housing, hospitals, schools and on major construction sites for companies in the foreign direct investment sector such as Facebook's new premises in Ballsbridge in Dublin.
As expected the Irish cabinet has also agreed that click and collect for non-essential retail will be replaced by click and delivery.
There are 921 people with Covid-19 in hospital in the Republic of Ireland, the highest number since the start of the pandemic, the chief executive of the Health Service Executive has said.
"Healthy people are getting very sick. Everyone gets how serious this is now.
"Let's all do what's needed, turn this around, save lives, whilst the vaccine arrives," tweeted Paul Reid.
Irish Justice Minister Helen McEntee has revealed she has tested positive for Covid-19.
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She tweeted on Wednesday that in line with government guidance she is now "isolating".
Last month, Ms McEntee became the country's first serving cabinet member to announce she was pregnant while in office.
The previous highest level of hospital admissions in the Irish Republic was 881 on 15 April last year.