Three women have been killed and two children taken to hospital with serious injuries following separate crashes in Cork and Waterford.
Two women, one in her 40s and another in her 60s, died in the Cork crash.
They were the drivers of two vehicles involved in a collision at Navigation Road on the main Mallow to Killarney Road, the N72, at about 3.45pm on Sunday.
Emergency services arrived quickly but both women were pronounced dead at the scene.
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Two children, a boy and a girl aged five and eight years, were passengers in the car being driven by their mother – the woman in her 40s – and they were both rushed by ambulance to Cork University Hospital.
The woman in her 60s was the sole occupant of the other car.
It is understood both women who lost their lives are from North Cork but gardaí are not releasing their names until relatives are notified.
Gardaí have closed the road and put diversions in place. The road is likely to remain closed for several hours to allow a forensic crash investigator examine the scene of the collision.
Separately, a woman in her 60s died following a three-vehicle collision on the N25 at Moonameen, Co Waterford, about 2.10pm on Sunday.
Gardaí and emergency services attended the scene, but a woman who was travelling as a passenger in one of the cars was pronounced dead at the scene.
Her body has since been removed to the mortuary at University Hospital Waterford where a postmortem will take place.
The driver and passenger of the second car, a man and woman aged in their 50s, were taken to University Hospital Waterford for treatment of serious injuries, believed to be non-life-threatening.
The female driver of the third car, aged in her 60s, was brought by air ambulance to Cork University Hospital for treatment of serious injuries, believed to be non-life-threatening.
The road is currently closed for technical examination by Garda forensic collision investigators, with diversions in place.
Gardaí are appealing for witnesses.
Meanwhile a man who died in a single-vehicle crash in Co Donegal on Saturday afternoon has been named locally.
He was Danny Gallagher from The Glebe in Downings.
Aged in his 70s, he was the driver of a van which crashed on the R245 outside Carrigart on the Milford Road at about 1pm. He was pronounced dead at the scene.
His body has since been removed to the mortuary at Letterkenny University Hospital for a postmortem.
The road was closed for technical examination by gardaí, with diversions in place.
Gardaí are appealing for witnesses.
In Northern Ireland a man in his 40s was arrested on suspicion of dangerous driving on Saturday afternoon after colliding with several cars while travelling on the wrong side of the road outside Bangor, Co Down.
Police on patrol heading on the Belfast Road towards Bangor observed a vehicle travelling towards them on the wrong side of the A2 dual carriageway around 11.25am. Officers signalled for the driver to stop but he failed to do so and continued towards Belfast.
Several members of the public reported their cars were damaged by this vehicle before the driver was later stopped. Two people attended hospital for assessment.