St Vincent’s University Hospital in Dublin is appealing to the public to avoid its emergency department.
The south Dublin hospital said services are under "extreme pressure" due to the high number of patients attending the emergency department.
In a statement, it appealed to patients who do not need emergency care to contact their GP.
Any patient who is in need of emergency hospital care will be seen and the hospital urged such patients not to delay and to seek care.
The move comes amid increasing transmission of Covid-19 in Ireland, with the number of detected and reported cases and hospital admissions increasing in recent days.
An increase in Covid cases in intensive care is being monitored by the Department of Health.
Minister for Health Stephen Donnelly told Cabinet on Tuesday that Covid is expected to continue to pose challenges to health and social care services.