Suspected explosive devices sent to armed forces recruitment offices bear “hallmarks of Northern Ireland-related terrorism”, a Number 10 spokeswoman said last night.
Sources said one of the suspicious packages discovered was stamped with a Republic of Ireland postmark but no specific group had claimed responsibility for the attack.
Prime Minister David Cameron chaired a meeting of the Government’s Cobra emergencies committee to discuss the suspicious parcels, which sources said were “crude” in design but “could have caused injury to others”.
A Number 10 spokeswoman said: “Seven suspect packages have been identified as containing small, crude, but potentially viable devices bearing the hallmarks of Northern Ireland-related terrorism.
“These have now been safely dealt with by the police and bomb disposal units.
“Guidance has been issued to staff at all military establishments and Royal Mail asking them to be extra vigilant and to look out for any suspect packages and the screening procedures for mail to armed forces careers offices is being reviewed.
“The national threat level remains under constant review.”
Four parcels were discovered at army careers offices in Oxford, Brighton, Canterbury and the Queensmere shopping centre in Slough which was evacuated , counter-terrorism police officers said.
One package was found in Aldershot, Hampshire, yesterday, while two packets were found on Tuesday at the armed forces careers office in Reading, Berkshire, and the Army and RAF careers office in Chatham, Kent, the South East Counter Terrorism Unit (Sectu) said.
Ministry of Defence bomb disposal units were called, although this is routine with such packages.
Sources in Dublin indicated that two of the seven low-grade explosive parcels were sent from the island of Ireland.
The others, it is understood, were delivered from different locations within Britain.
Although they were not sophisticated, they were described as viable.
While no group has yet to claim responsibility, it is believed dissident republicans opposed to the peace process were behind the intimidation attempt.
The official threat level for terrorism is set separately for Northern Ireland and the British mainland.
At the moment the threat level in Northern Ireland is rated “severe” and in Great Britain “moderate”, which means an attack is thought possible.