A countrywide restriction on household visits is in effect for four weeks as part of efforts to contain the spread of Covid-19.
Since midnight, Cavan, Donegal and Monaghan have also been moved to Level 4 restrictions as part of measures announced by the Government.
It comes after it was confirmed that three more people with the virus had died and 1,205 new cases were announced yesterday evening.
Across the country there are restrictions on visits to homes and gardens except on compassionate grounds or for essential reasons, such as providing care to children, elderly or vulnerable people, and in particular those who live alone.
In the three counties where Level 4 is in operation, restrictions mean that non-essential retail and personal services have had to close.
Bars, cafes and restaurants can still serve up to 15 people outdoors, but from Monday weddings will be reduced to a limit of six guests.
The measures will remain in place until at least 10 November.
Yesterday evening, the Chief Medical Officer said it is now clear Covid-19 is not in control, with the disease trajectory nationally rapidly deteriorating.
Dr Tony Holohan said the virus growth rate has accelerated and is a matter of grave concern, as he again appealed to people to cut non-essential social contacts with others.