Prison officers in Northern Ireland have returned to normal duties on Saturday after taking part in unofficial strike action.

On Friday morning, for the second time this week, officers either telephoned to say they were sick or came to work and left shortly afterwards, saying they were sick.

The same happened as the night shift was due to clock on.

The protest action has followed a dispute over security measures being offered to officers following the discovery of staff details on a laptop computer during a police investigation into an alleged IRA spy ring Stormont.

Peter Russell: "Strike will achieve nothing"

Police officers were called in to staff the prisons for the second day of action, stretching the service, which is also being required to support security force personnel providing firefighting cover during the firefighters' strike, which started on Friday morning.

The director general of the Prison Service Peter Russell said more than 90% of prison officers were involved in the action.

All visits were cancelled and there was considerable disruption to the daily routine of inmates at Northern Ireland's prisons - Maghaberry in County Antrim, Magiligan in County Londonderry and Hydebank Young Offenders' Centre in Belfast.

On Friday afternoon, inmates in a wing of Magaberry refused to co-operate with prison procedures by going into their cells.

Earlier action

On Wednesday, 600 officers failed to come to work or clocked on, and then went home after an hour saying they were sick.

Police spent the night guarding Maghaberry and Magilligan jails.

Prison Officers' Association chairman Finlay Spratt said POA members were angry at what they said was the government's failure to provide them with adequate funds to upgrade home security.

This followed the discovery of 1,400 officers' names on a list recovered during an investigation into alleged IRA intelligence gathering.

The Prison Service director general said nothing would be achieved by the unofficial action.

Mr Russell said there was no doubt that the 600 prison officers who either reported they were sick or came to work on Wednesday and then went home sick, were engaging in pre-planned, co-ordinated action.

It is illegal for the officers to go on strike.