Police have named one of two men who lost their lives on the roads over the weekend as 79-year-old Patrick James McGeough from the Monaghan area.
Three men were involved in serious road collisions over the weekend - two of them died and a third is critical but stable.
Mr McGeough lost his life in an accident on the A3 Cavan Road, near Newtownbutler in Fermanagh on Saturday
The road was closed on both sides of the border.
A second man in his forties died in a separate crash on the Clooney Road in Londonderry on Sunday morning.
A man and woman aged in their fifties were taken to hospital for treatment to non-life threatening injuries after the Londonderry collision.
Police said a silver coloured Ford Ka and a grey coloured Peugeot 308 were involved in the incident and asked for witnesses to come forward.
The Clooney Road was closed while police investigated.
DUP MLA for Foyle, Gary Middleton, expressed his condolences to the family of the deceased man.
“[My] thoughts and prayers are with the family of the man who died following a RTC on Clooney Road. Wishing the injured a speedy recovery,” said Mr. Middleton.
SDLP MLA for Foyle, Mark H. Durkan, described the incident as “tragic”.
It happened just after midnight between the Maydown and Gransha roundabouts, he said.
“My thoughts and the thoughts of all my SDLP colleagues in Derry, are with the friends and family of this man and indeed with the friends and families of those injured in this accident. I travel this stretch of road everyday and know just how dangerous this junction can be.
“I believe the occupants of the other car have suffered significant injuries which thankfully are non-life threatening.
“It is of course a traumatic experience for all involved and I sincerely hope they make a quick and thorough recovery,” he added.
Meanwhile a 19-year-old man was left in a stable but critical condition in hospital after a one-vehicle crash in Ballywalter on the Ards Peninsula.
Police said the crash happened at about 4.50pm on Saturday on the Dunover Road. The road was closed in both directions while officers investigated the scene.