Royal Mail staff suspended all deliveries on Saturday following an alleged threat against a worker. Collections were also disrupted.

Meanwhile, the police are investigating reports of murder threats against managers and staff at the Royal and Mater hospitals in Belfast.

A statement from the Royal group of hospitals said the police were called in after telephone threats were made against three unnamed workers at each hospital with affiliations to the security forces.

Management and senior trade union officials have unanimously condemned the threats.

They described them as "totally unacceptable" and called on the public to voice their concerns on behalf of health workers.

Emergency meeting

A union representative for the postal workers said the situation would be reviewed on Monday morning.

The Royal Mail said the police were investigating the reports.

Workers at the Great James Street Sorting Office will be holding an emergency meeting at 0500 BST on Monday to discuss the situation.

In a statement, the Royal Mail said it provided an essential public service to all sections of the community and took the security of its staff extremely seriously.

Charlie Kelly from the Communication Workers' Union said staff were very concerned.

The health and safety of our members is far more important than the price of a first class stamp

Charlie Kelly Communication Workers' Union

"Staff are worried - especially in light of events this week," he said.

"We had these threats after young Daniel McColgan got killed and we have had previous threats.

"Because of the time we are out on the streets in the morning we are in the frontline and we are seen as easy targets.

"Unfortunately at the minute - while the staff apologise for any inconvenience to the members of the public in Derry - we would hope we could resume on Monday morning.

"But the health and safety of our members is far more important than the price of a first class stamp."

Disrupted

In February, postal deliveries in Londonderry were once again disrupted after a threatening letter, purporting to come from loyalists, was sent to staff.

The letter named 11 people - five Catholic and four Protestant postal workers and two members of management, one Catholic and one Protestant.

The letter - which was signed "Waterside Young Loyalists" - warned the 11 workers not to enter the largely Protestant Waterside area of the city.

Staff in the city have already gone on strike twice this year.

Mail deliveries in the city were disrupted when workers walked out in February after a Catholic postman was warned to stay out of the Waterside area.

That threat came just three weeks after postal workers walked out in protest at the Ulster Defence Association murder of Catholic postman Daniel McColgan near Belfast, and also threats made to Catholic postal workers