A group calling itself the IRA has claimed responsibility for suspect packages sent to armed forces recruitment centres in the UK last week.
Scotland Yard said a group using a recognised codeword had contacted a media outlet in Northern Ireland on Saturday.
Four suspected explosive devices were discovered at Army careers offices in Oxford, Brighton, Canterbury and the Queensmere shopping centre in Slough last Thursday.
This followed packets sent to Aldershot, Hampshire, on Wednesday and another two on Tuesday to an armed forces careers office in Reading, Berkshire, and the Army and RAF careers office in Chatham, Kent.