A 36 year old man has been charged in connection with the investigation into the fatal stabbing of a 55 year old woman in Waterford last night.

He's being detained at Waterford Garda Station this evening and will appear before a special sitting of the District Court tomorrow.

Maria O' Brien died after she was attacked on the grounds at St Otterans psychiatric hospital in the city at around 7 O' clock last night.

A 36 year old man, who was also a patient at the hospital, was arrested and has since been charged in connection with this investigation.

Another patient and staff member were also injured during the attack, they're being treated for non-life threatening injuries.

A post mortem was carried out on Ms O' Brien's body this afternoon at University Hospital Waterford - the results of which are expected to be released later.

Both the Gardai and the HSE are carrying out separate investigations.

The General Secretary of the Psychiatric Nurses Association has praised the staff at St Otterans for their bravery in dealing with a situation last night.

Des Kavanagh, says there now needs to be a full review of mental health services in Ireland.