Gardaí have urged motorists to drive with care after four people were killed in separate crashes in Donegal and Laois. A fifth person died in a road crash in Co Down.
Met Éireann has said temperatures could drop to -5 in some areas with widespread severe frost and icy patches.
Two men died in a crash in Burt, Co Donegal, on the Derry to Letterkenny road this morning.
The men, aged 55 and 24, were pronounced dead at the scene. The driver and sole occupant of the second car, a 59-year-old woman, was taken to Letterkenny General Hospital where she is described as being in a stable condition.
Also in Donegal, a pedestrian was involved in a collision with a car at Carraig Airt. The accident happened at around 7.40pm last night.
The 60-year-old man died while being transported to hospital. The occupants of the vehicle were uninjured.
The road was closed for a forensic collision examination but has since re-opened.
Meanwhile, a 26-year-old man died in a single-vehicle crash on the M7 in Co Laois.
The accident happened at around 8.20am this morning at the Killenard/Mountmellick exit.
Elsewhere, a 37-year-old man died after his tractor crashed in Co Down.
The accident happened on the Banbridge Road in Dromara. The tractor was the only vehicle involved in the crash.
A man in his 20s is in a serious condition in hospital in Tralee, Co Kerry, after the car in which he and another man were travelling crashed around 8km outside Kenmare in the early hours of this morning.
The second man was not seriously injured.
The single-vehicle crash happened after the car went out of control and hit a wall and a tree near Bonane at around 3.30am.
Both men were taken to Kerry General Hospital in Tralee.
