Scotland Yard says terror group used recognised codeword to claim responsibility for sending packages to offices in Britain

The republican terror alliance known as the new IRA has said it was responsible for a series of parcel bombs sent to army recruitment offices across England.

Scotland Yard has confirmed that the new IRA used a recognised codeword in claiming responsibility for sending the suspect packages to military careers offices in Oxford, Brighton, Canterbury and the Queensmere shopping centre in Slough last week.

Earlier the terror group had sent similar packets to Aldershort, Reading and the RAF careers office in Chatham, Kent. A number of the packages had Dublin postmarks on them and were thought to contain low grade explosives.

The shopping centre at Queensmere was temporarily evacuated, while cordons were placed close to all the offices where packages have been found. Ministry of Defence bomb disposal units were also called in to deal with the devices.

In a coded statement to Belfast newspaper, The Irish News, the terror group said: "The IRA claims responsibility for the explosive devices that were sent to British armed forces recruitment centres in England. Attacks will continue when and where the IRA see fit."

The parcel bombs mark a fresh phase in the new IRA's armed campaign by targeting mainland Britain. Dissident republican organisations have not struck in England for almost a decade.

There have been a series of arrests made among all three anti-process republican groups – the new IRA, the Continuity IRA and Oglaigh na hEireann – over the past 12 months and security forces on both sides of the Irish border have thwarted at least half a dozen attempts to transport bombs and mortar devices into Belfast and Derry .

A spokesperson for Scotland Yard said: "We are aware of the claim of responsibility for the devices that were sent to Army recruitment centres in England last week.

"The claim was received on Saturday 15 February by a Northern Irish media outlet using a recognised codeword. The claim was allegedly made on behalf of the 'IRA'.

Northern Ireland's deputy First Minister Martin McGuinness condemned those on the republican side still wedded to violence. He said pipe bombs and letter bombs were an "attack on the peace process".

McGuinness, Sinn Fein's chief negotiator during the peace process, wrote on Twitter: "Those responsible belong to the past. Their futile acts must be condemned."

Sending parcel and letter bombs is an old tactic that goes back to the Provisional IRA's terror campaigns of the early 1970s. In the first phase of PIRA's "armed struggle" the organisation posted suspect devices in parcels to a range of targets including 10 Downing Street as well as senior military and police officers.

The new IRA was formed in the summer of 2012 by the merger of the Real IRA, an armed vigilante group known as Republican Action Against Drugs and independent armed republican units in Co.Tyrone. They released a statement to the Guardian confirming that they were now to be known as the IRA and vowed to continue "armed struggle" against the Northern Ireland state and the British government, and its armed forces.

Critics of Sinn Fein's political strategy who are deemed "political dissidents" have been trying recently to persuade the armed groups to give up their campaigns. In January, former IRA hunger striker Gerard Hodgins warned the dissidents that Britain had its "eyes and ears" on their organisations through technical surveillance and informants on a 24/7 basis.

Detective Superintendent Stan Gilmour of the South East Counter Terrorism Unit (Sectu), last week said the contents of the packages sent to army recruitment offices were "suspicious in nature" and would be forensically examined. But he added: "Even if the contents are determined to be a viable device, they pose a very low-level threat and are unlikely to cause significant harm or damage."

Advice has been sent to the Royal Mail and to the Ministry of Defence to ensure that staff ''remain vigilant'', he added.

A spokesperson for Scotland Yard said: "The public is urged to remain vigilant and report anything suspicious to the Anti-Terrorist Hotline: 0800 789 321."