Two men, aged 35 and 46, and two women, aged 21 and 44, were arrested in Londonderry on Wednesday in connection to the letter bombs that were sent over a number of months from late 2013 to earlier this year.
The letter bombs were addressed to senior police and army officials but they were intercepted by staff at the Royal Mail sorting offices in Northern Ireland before they could reach their intended recipients and none were activated.
The suspects are alleged to be connected to the New IRA, a dissident republican paramilitary group opposed to the Good Friday Agreement and the demilitarisation of the Provisional IRA, which formed as a merger between the Real IRA, the Republican Action Against Drugs (RAAD), and a number of other smaller paramilitary groups in 2012. The New IRA, along with the Continuity IRA and other republican paramilitary groups, may be small and marginalised, but they maintain the ability to carry out low-level attacks against supporters of the agreement.
The arrests were made by the Serious Crime Branch of the Police Service of Northern Ireland (PSNI), with the investigators working closely with England’s South East Counter Terrorism Unit (SECTU).
The suspects are being questioned about the letter bomb campaign the high-security Antrim police station, as well as other letter bombs sent to army recruitment offices across England in recent months.