Counter-terrorism police are investigating reports of suspect packages being found at army careers offices.
Packages have been found in Canterbury, Oxford, Slough and Brighton, while similar packages were found earlier in the week in Aldershot, Reading and Chatham, the south east counter terrorism unit said.
Police officers consider the situation a "low-level threat" but "viable", sources said.
More top news
Low-paid healthcare workers are having to pay the "extortionate" fees to park in front of their workplaces, a study shows.
After a cold start on Wednesday, it will be another day of sunshine and showers across many central and eastern parts.
It is claimed that both police and security services, including MI5, have been prevented from vast pools of data on the social media site.