The IT systems at the Coombe Hospital in Dublin have been locked down as an investigation begins into a cyber attack.
In a statement, the Coombe Women and Infants University Hospital confirmed it had been the subject of a cyber attack overnight.
It said services are continuing as normal, but its IT systems are locked down on a "precautionary basis".
The hospital said it is working with the Health Service Executive to resolve the matter.
The HSE said its teams are working with colleagues in the Coombe and have disconnected the facility from the National Health Network.
The HSE said the attack has impacted several systems in the hospital.
"At this point we have not seen evidence of an impact external to the Coombe hospital but we are continuing, with external support, to assess whether there is any broader impact. We will share further information as we have it," the HSE said.
Minister of State Ossian Smyth has described the cyberattack as "serious" and said the National Cyber Security Centre and the Garda National Crime Bureau are involved.
"We don't know if there has been any data breach so far - whether there are any data protection issues involved. That's all being assessed," he said.
The minister said the attack has "the hall marks of a ransomware attack" in that it involves encryption of servers.
However, he added: "There hasn't been any note. In the previous attack on the HSE there was a ransomware note on every machine that was compromised.
"That hasn't been the case here ... It's also not clear whether it is a human operated ransomware attack or if it was a self-replicating attack, which is much less serious."
The hack was focused on the IT system of the Coombe, not the HSE.
Additional reporting Paul Cunningham