Gardaí investigating the killing of Detective Garda Adrian Donohoe have appealed to those who know the people involved in the murder to tell the truth about what happened.

Chief Superintendent Christopher Mangan said that the minds of those who gave emotional and logistical support to those involved would never be at peace until they come forward.

He said it was not too late to do the right thing.

The appeal came on the fifth anniversary of the shooting dead of the detective outside the Lordship Credit Union in Bellurgan in Co Louth.

Gardaí said the suspects were known to them and Chief Supt Mangan said that some have left the country and sought protection in other jurisdictions.

However, he said that would not stop gardaí following them "to the ends of the earth" to bring them to justice.

He said gardaí had received significant information from members of the public, particularly in the past year, and that has led to a considerable number of lines of inquiry.

Gardaí are making progress, he said, but he could not go into any finer detail without compromising the investigation. 

He also said that the sense of loss, sadness and grief about Det Garda Donohoe's death will never leave his family, friends and the local community, but that gardaí will never cease in their efforts to solve his murder. 

Chief Supt Mangan said Det Garda Donohoe had lost his life while protecting other people in the community and appealed to people with information, no matter how trivial or insignificant, to contact gardaí.

He said that they would be treated with the strictest of confidence. 

Anyone with relevant information can contact gardaí in Dundalk on 042 9388470 or the Garda Confidential Line on 1800 666 111.