Health service IT systems could take days to return to normal, following a cyber attack this morning.
The HSE says thousands of appointments might have to be cancelled if the problem continues into next week.
Some maternity and cancer services have been impacted and there are delays to appointments that do go ahead.
The system to refer people for a Covid test and the portal to register for a vaccine are both down.
HSE Chief Operations Officer, Anne O'Connor, says the attack came out of the blue:
The attack has caused some disruption at Cavan and Monaghan Hospitals also.
The Rotunda Hospital has cancelled most outpatient appointments, except for heavily pregnant women.
The National Ambulance Service isn't affected - and HSE chief executive Paul Reid says neither are Covid vaccinations:
