The Health Service Executive has said that 50 agency nurses did not present for work today under new contracts which offer lower rates of pay to staff.
In a statement, the HSE said that hospitals around the country remained under pressure. However, it said that there had been "no significant impact on patient services and no risk to patient safety".
Cavan General Hospital has cancelled elective or non-urgent surgery although the HSE said that this remained under consideration in a number of other centres.
The HSE said that it was continuing to monitor the situation closely and would put contingency arrangements in place as required.
The row centres on a move by the HSE to introduce new arrangements for securing nurses from agencies.
It has said that these new measures will generate savings of up to €40 million. However, unions have argued that the rates being paid to members working for agencies under the new contractual arrangements with the HSE are considerably lower than those which applied up to now.
In a message broadcast on its website, the Irish Nurses and Midwives Organisation urged its members not to make themselves available on the new lower rates.
The union said that if members agreed to work for the reduced rates, there would be pressure on them to accept even lower pay scales in the future.
Nursing unions said yesterday some services were affected in Cork, in the midlands and in Limerick. At Cork University Maternity Hospital, 14 of the 16 agency midwives due to work yesterday made themselves unavailable for duty .
The HSE said patient services had not been affected as management had redeployed staff from other parts of the hospital. It also said some nurse managers had also been called in to discharge duties.