Northern Ireland security forces on Tuesday defused a large explosive device close to the border with the Irish Republic, which police believe was planted by dissident republicans opposed to the region’s two-year-old power sharing agreement.

The roadside device, made up of 600lb of homemade explosives, was as large as the bomb used by the Real IRA in Omagh in 1998 which killed 29 people, the single worst atrocity in Northern Ireland’s 30-year long Troubles.