At least four hospital Emergency Departments have been hit by unofficial industrial action taken by locum doctors.
The Irish Association for Emergency Medicine says it is concerned for patient safety after a number of agency doctors did not turn up for work today in a row over reduced pay.
The IAEM fears the dispute will escalate and affect more hospitals across the country over the coming days.
It follows the introduction of a new framework agreement governing the provision of short term/temporary medical agency placements.
As part of the new arrangements payments to agency doctors are to be reduced from €40 to €34 per hour.
The HSE says this new framework was deemed necessary for a number of reasons but in particular to bring greater equity to pay between agency staff and those who are employed by the HSE.
In a statement this evening, the HSE said this disparity has caused considerable difficulty in retaining doctors and nurses within the system.
The HSE said it has been advised that a small number of agency medical staff have indicated that they may not turn up for their rostered duty this week.
It said there are well-established and agreed procedures to deal with this to ensure continuity of care to patients and clients.
"The HSE is working with Hospital Groups in order to ensure that all possible arrangements to support the continued delivery of care on a contingency basis.
"Hospitals will continue to work with the contracted employment agencies to source staff and will continue to assess the position over the coming days," the statement said.