The New IRA is thought to have acquired Russian grenades stolen from the front line of the war in Ukraine.

Counter-terrorism officers in Northern Ireland seized weapons including plastic explosives and the grenades in Londonderry on Thursday.

“These items are military grade, and we believe the intention was to mount attacks in an attempt to kill police officers,” said Mark McEwan, the assistant chief constable.

Two men and a woman were arrested in the raids, which followed intelligence that the terror group had obtained the arms and was planning to attack a police officer. 

The arrests triggered riots, which led to 16 officers being injured. The unrest continued for a second night on Friday, with petrol bombs being thrown at Police Service of Northern Ireland (PSNI) Land Rovers.

Officers seized two hand grenades, a handgun, more than 50 rounds of ammunition and over a kilogram of plastic explosives, as well as more than £2,000 in cash.