Residents of Kildare, Offaly and Laois will not be permitted to travel outside of their counties except for in limited circumstances, under plans agreed by the Irish government.
There have been 226 cases of Covid-19 in the last 14 days in the counties.
He urged people to live the words of the late SDLP leader John Hume, who said "Solidarity is strength".
The Irish health authorities had earlier voiced concern at the current Covid-19 infection rate in the country, particularly in Kildare, Laois and Offaly.
The acting chief medical officer said the volume of cases in the three counties was "significant" and he urged vigilance.New restrictions for residents of three counties.
One Kildare employer, O'Brien Fine Foods in Timahoe, confirmed it has suspended operations after 80 of its staff tested positive for Covid-19
Acting Chief Medical Officer Dr Ronan Glynn urged people in Kildare, Laois and Offaly to "remain vigilant to stop the further spread of Covid-19 in these areas"
"While the majority of these cases can be accounted for by outbreaks, this volume of cases is significant and our main priority now is to ensure that these outbreaks do not lead to widespread community transmission in the region," Dr Glynn said
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