Dissident republicans have been blamed for leaving a car containing a 180kg bomb outside the Policing Board's headquarters in Northern Ireland.
The car was driven through a barrier by two men who ran off before the device partially exploded in Belfast on Sunday night.
Four men have been arrested following a gun attack on police officers west of Belfast, also thought to be by dissident republicans.
This month, the Independent Monitoring Commission reported the dissident republican threat in Northern Ireland is at its highest level for almost six years.
It says the two main groups, the Real IRA and the Continuity IRA, are working closely together to increase the threat to security forces.
The Police Board is an organisation that monitors policing as part of the peace process in Northern Ireland.