A teenager is among four men killed in a spate of crashes within hours of each other.
Two men, one in his late teens and one in his 20s, died when the car they were travelling in collided head-on with a van in Co Donegal, gardai said.
It is believed they were driving in the wrong direction - outbound - on the inbound section of the N13 dual carriageway into Letterkenny.
Gardai said they are investigating all the circumstances surrounding the incident and have appealed for witnesses.
The crash happened at about 4.45am on Wednesday.
The two victims were pronounced dead at the scene.
The driver of the van, a 40-year-old man, was taken by ambulance to University Hospital in Letterkenny. His injuries are not thought to be life-threatening.
Elsewhere, a 42-year-old driver was seriously injured in a head-on crash between two cars in Dunboyne, Co Meath.
The collision happened at Castlefarm on the main Dunboyne to Maynooth road at around 8.50pm on Tuesday.
The male driver was taken by ambulance to Connolly Hospital in Dublin, where he was later pronounced dead. He was the sole occupant of the car.
The driver and four passengers in the second car were also taken to hospital. Their injuries are not believed to be life-threatening.
Separately, a man in his 20s was killed in a crash near Kilcock in Co Kildare.
The car he was driving collided with a truck on the Clane to Kilcock road, near Baltracey, at around 11.30pm on Tuesday, gardai said.
The man was pronounced dead at the scene. No-one else was in the car.
The driver of the truck was taken to Blanchardstown Hospital with what are described as minor injuries.
The spate of deaths came hours after road safety chiefs warned of an increase in fatal collisions around the country.
The Garda and Road Safety Authority revealed on Tuesday an 8% jump in road deaths since the same time last year.