Six held after security breach

Castlereagh is the PSNI's Belfast headquarters

Six people have been arrested in connection with a security breach at Belfast's police headquarters which security sources are linking to the Provisional IRA.

A Special Branch officer was assaulted and documents taken when three men entered an office inside the Castlereagh complex, in the east of the city, on St Patrick's Day.

The theft occured in the source handling unit, which is used as a "link-point" for security force informers and their police handlers.

The security force's actions are extremely provocative to republicans

Alex Maskey
Sinn Fein

The police investigation is now concentrating on the possibility of republican involvement, specifically the Provisional IRA, security sources have told the BBC.

On Saturday, detailed searches involving the police and army were carried out at premises in west, north and east Belfast and in Londonderry.

A police spokesperson confirmed six people had been arrested, following operations involving more than 200 police officers and several hundred soldiers.

It is understood one of those arrested was a former IRA prisoner Bobby Storey.

None of those arrested, four men and two women, is connected to the security forces.

A civilian employed at Castlereagh was also being held.

Bobby Storey: Among those arrested

BBC Northern Ireland chief security correspondent Brian Rowan said: "This is the latest twist in the Castlereagh incident which up to this point had all the appearance of an inside job."

One man was arrested at his home in Limewood Street in Derry during a search involving forensic officers.

Local republicans said the police searched the offices of Tar Abhaile, a group set up to support former republican prisoners.

It is understood material was taken away from both premises.

The police said a number of people had been arrested in the Bogside area of the city.

A number of premises were raided

A Sinn Fein spokesman said republicans had played "no part in the raid on Castlereagh".

He said it was an "inside job" and claimed the arrests were an "attempt by Special Branch to cover up the truth".

West Belfast Sinn Fein assembly member Alex Maskey said the arrests would "seem to suggest that there is panic going on within the security services about this break-in".

"The security force's actions are extremely provocative to republicans when you consider that this Easter weekend people all over Ireland will be commemorating their history, culture and heritage," he added.

Days after the breach, it emerged that the office was only moved to that room from another part of the building a week previously because the complex was being refurbished.

Two separate investigations into the incident are taking place - the police's own and an inquiry by former senior civil servant Sir John Chilcot who will report directly to Northern Ireland Secretary John Reid.

When he announced his independent review, Dr Reid said it would establish how the security breach happened, what damage it did to national security and whether measures taken in response were adequate.

Sir John Chilcot will be assisted by Colin Smith, a former Thames Valley chief constable and a former member of Her Majesty's Inspectorate of Constabulary.

Anti-terrorism

The review will proceed in parallel with the criminal investigation which is being led by Detective Chief Superintendent Phil Wright, the most senior detective in Belfast.

Northern Ireland Police Ombudsman Nuala O'Loan has said her office would not carry out any investigation into the breach at this stage.

Northern Ireland Chief Constable Sir Ronnie Flanagan has said the documents stolen did not include the names of security force informers.

Special Branch deals with intelligence work, some relating to informers, and has an anti-terrorism role in Northern Ireland.

One of the main police centres for the interrogation of terrorist suspects was located at Castlereagh. It closed at the end of 1999.