Five men have been arrested in Londonderry over the murder of an RUC officer in 1993 and the attempted murder of a police officer in April.
Two men, aged 48 and 59, were arrested over the 1993 murder of Constable Michael Ferguson in Derry.
Three men, aged 23, 52 and 62 were arrested over a bomb which was left near a policewoman’s car in Dungiven, County Londonderry, on 19 April.
All five were taken to Musgrave Police Station in Belfast for questioning.
The 52-year-old man is also being questioned as part of Operation Ledging, targeting the New IRA’s bomb making activities as well as the group’s storage of explosive devices and equipment.
The 59-year-old and 62-year-old will also be questioned by detectives from Operation Kenova in connection with other historical matters.
Royal Ulster Constabulary (RUC) officer Constable Ferguson, from Omagh, was shot twice, at close range, in the back of the head by an IRA gunman in Shipquay Street in Derry on 23 January 1993.
The Catholic policeman, who was 21, was on duty at the time and was taken to Altnagevlin Hospital but died from his injuries.
The explosive device dicsovered by police in April was found attached to a container of flammable liquid close to a Police Service of Northern Ireland officer’s car.
Detectives believe the New IRA was responsible for what it described as an attempt to kill the officer and her young daughter.