Health Minister Leo Varadkar has said 10 Galway psychiatric nurses who refused to go on duty this morning over what they say are unsafe working conditions have put patients at risk.

The Psychiatric Nurses Association claims there have been 36 assaults on staff at the unit in the University College Hospital since the start of the year.

It says staff shortages mean the nurses had no option but to protest over the situation.

However, Health Minister Leo Varadkar said the unannounced action was not appropriate.

"I'm sure the nurses concerned have a legitimate grievance, but there's an appropriate way to deal with grievances like this," he said.

"(This) was unofficial, unannounced action and that by its very nature puts patient safety at risk. (It also) puts the other staff at risk, who were working the nightshift and now have to keep working."