Scotland Yard has confirmed that the new IRA used a recognised codeword to claim responsibility for sending packages to military career offices in Oxford, Brighton, Canterbury and the Queensmere shopping centre in Slough last week.
Earlier they had sent similar packets to Aldershot, Reading and the RAF careers office in Chatham, Kent.
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’.
“The public is urged to remain vigilant and report anything suspicious to the anti-terrorist hotline, 0800 789 321.”
The new IRA came into existence in the summer of 2012 when the Real IRA merged wit armed vigilante group Republican Action Against Drugs and independent armed republican units in County Tyrone.
They released a statement to the Guardian confirming that they were now to be known as the IRA and vowed to continue the “armed struggle” against the Northern Ireland state and the British government, and its armed forces.
They ambushed and shot David Black, a Northern Ireland prison officer on Northern Ireland’s M1 motorway in November 2012.