- 18 updates
Queensmere Shopping Centre, in Slough, was evacuated, a spokesman for the centre confirmed, while St Giles in Oxford was closed.
It is understood a suspicious package was also reported at the army careers office in St Peters Street, in Canterbury, Kent.
Officers have set up a police cordon and shoppers are being told to avoid the area, the Kentish Gazette reported.
The Ministry of Defence have said they are aware of ongoing security incidents at various Army Career offices.
A Ministry of Defence spokesman said: "We can confirm that we are aware of security incidents ongoing in Oxford, Slough and Brighton involving armed forces careers offices.
"The relevant police authorities are investigating with military EOD (explosive ordnance disposal) teams in support and any further inquiries should be directed to the police.
"Security advice has been reiterated to our personnel."
Staff were warned to be extra vigilant after suspicious packages were found at various Army Career offices yesterday, counter-terrorism police said.
Detective Superintendent Stan Gilmour, of the south east counter terrorism unit, said:
The South East Counter Terrorism Unit is currently investigating a number of suspect packages found outside Army Careers offices today.
The packages have been found at Army Career offices in St Giles in Oxford, Queensmere Shopping Centre in Slough and Queens Road in Brighton.
The contents of the packages are currently being assessed.
The MOD Bomb Disposal Units have been called, as in any suspect packages that are found.
A number of packages were also found yesterday at Army Careers offices in Aldershot, Reading and Chatham.
A number of roads in Brighton have been closed after police were alerted to a suspicious package in Queen's Road, Brighton.
Queen's Road is sealed off between North Road and North Street, and neighbouring streets are also closed, including Spring Gardens, Kew Street, Zion Gardens, Windsor Street, Titchbourne Street and Church Street.