The Health Service Executive remains very compromised following the cyber attack on its IT systems, but some progress is being made, according to Chief Operations Officer Anne O'Connor.
The HSE was forced to shut down all of its IT systems earlier this month following the "significant" ransomware attack, which focused on accessing data stored on central servers.
Speaking on RTÉ's Morning Ireland programme, Ms O’Connor said progress in restoring systems is "site specific" and critical services such as radiotherapy and labs remain compromised.
She said outpatient services also remain significantly impacted and will operate at around 40% capacity this week.
Chemotherapy services have resumed and sites at St Luke's, St James's and St Vincent's hospitals in Dublin are operational.
However, sites in Galway and Cork are not operational and this is an absolute priority, Ms O’Connor said, adding that people are travelling to Dublin for treatment, while arrangements have also been made with private hospitals.
Ms O'Connor said hospitals in the south and west remain heavily impacted and said she hopes some progress will be made over the next day or two, but the process has "not gone as smoothly as hoped."
She said efforts are being made in the broader system to allow staff access to email and therefore improve communications.
Meanwhile, the Mercy University Hospital in Cork has said it is working with the HSE on restoring its computer systems, in a controlled and safe manner.
Yesterday, the hospital secured a High Court injunction, stopping any sharing of any data stolen from its internal IT system, after receiving a ransom demand from hackers.
The Mercy Hospital is a voluntary, public and private hospital, with 325 beds and is not run by the HSE.
The cyber attack on the HSE on 14 May also hit the Mercy's public systems and was also found to have affected the hospital's internal IT system and it sought similar court orders to the HSE.
The hospital said that it took the action, due to the imminent threat of publication of confidential medical and personal data relating to individuals.
The Mercy said it continues to maintain essential services.
Additional reporting Fergal Bowers