The Police Service of Northern Ireland (PSNI) is "confident" that dissident republicans are in possession of the information leaked during last week's "significant" data breach.

“The picture in relation to last week’s data breach continues to evolve at pace," PSNI Chief Constable Simon Byrne said today, Monday, August 14.

“We are now confident that the workforce data set is in the hands of Dissident Republicans.

“It is now a planning assumption that they will use this list to generate fear and uncertainty as well as intimidating or targeting officers and staff.

“I won’t go into detail for operational reasons but we are working round the clock to assess the risk and take measures to mitigate it.

“Contrary to commentary circulating, we are not seeing any movement of officers or staff out of the organisation. I’d like to pay tribute to our people who have demonstrated tremendous resilience since news of this breach broke last week.

“Weekend events have shown their determination to stick to our values and continue to serve the public with commitment and professionalism.

“We are being strongly supported by a range of specialists from across the policing system in dealing with this unprecedented incident.

“We have measures in place to reassure and advise our workforce of what this risk means for them. 

“We will continue to liaise with the Policing Board, the UK Government and partners as we develop our response to this.

“The safety and welfare of our officers and staff remains my top priority.”

Byrne's comments come the same day that North Belfast Sinn Féin MLA Gerry Kelly, who is also on the Northern Ireland Policing Board, said that a "number of documents" was posted on a wall facing the Sinn Féin's office on Falls Road in Belfast.

"There was a photograph of myself and there was a statement saying, in large writing, 'Gerry, we know who your mates are now,'" Kelly said on Monday.

"And under that then there was what appeared to be and what turned out to be a section of the leaked documents that were put out."

Kelly said the documents did not have the names of the police officers involved, "but it had everything else."

He further said it was not the "whole 10,000," but it was a "substantial number."

Kelly said: "I look upon this as a deliberate threat by dissidents to me.

"I will not be intimidated, is the first thing.

"More serious, I think, is that this is the dissidents, or whoever is involved, putting out that their claim that they have access to the leaked documents, they are putting out a verification on that.

"I think that is their main intention in terms of what's happened here.

"But I will not be intimidated."

Kelly said he had been in touch with the police regarding the matter.

He further said: “We [Sinn Féin] represent the largest number of people in the nationalist areas, and we will not be intimidated by these small groups who have nothing to offer, who have minimal, if any, support in these actions."

Last week, the PSNI was rocked by an "extremely serious" data breach that saw information of some 10,000 officers and staff posted online for up to three hours on Tuesday, August 8.

The information that was posted online following a routine Freedom of Information (FoI) request included the surname, initials, rank/grade, role, and location of all serving officers and staff.

The following day, the PSNI said it was also investigating the circumstances surrounding the theft of documents, including a spreadsheet containing the names of over 200 serving officers and staff, along with a police issue laptop and radio, from a private vehicle in the Newtownabbey area on July 6.

On Thursday, Chief Constable Byrne said that the PSNI was investigating claims that dissident republicans were in possession of leaked information.