An explosion hit Northern Ireland near its border with the Republic of Ireland early on Monday.
It was the sixth such blast this year, targeting specifically officers, and marks the latest upsurge of violence to shake the troubled region.
Police said they suspected that the Continuity IRA or New IRA – two small Irish nationalist militant groups who claimed responsibility for previous attacks – were responsible for the explosion.
Northern Ireland deputy police chief Stephen Martin warned that the rising tensions could be attributed to the deadlock over Brexit, as the Irish backstop has arguably become the most crucial and alarming topic in the recent period.
Martin had no information linking the latest attack to Brexit, but stated that uncertainty over Brexit and Northern Ireland's suspended government coincided with the attacks.
There has been an increase in tensions in Northern Ireland in recent months with sporadic violence, much of it focused in Londonderry, also known as Derry. The incident came after a fatal shooting of a journalist during riots in the city of Londonderry.
Earlier in January, a car bomb exploded in the same city amid uncertainty over the future of the Irish border, as Brexit keeps adding to tensions in Northern Ireland. The New IRA was blamed for both attacks. It is regarded as the largest of the splinter dissident groups still operating and has been linked to several other killings in the past decade.