A 17-year-old boy from Limavady has died after a road accident near his County Londonderry home.
Keelen Mullen, from the Drumsurn area of Limavady, died after the car he was driving was involved in a crash with a tractor.
The collision happened on the Drumsurn Road, near the junction with the Cloghan Road, around 10.20am on Saturday.
Police have appealed for anyone who witnessed the crash to get in contact with them.
Meanwhile, in the republic, two young men and a toddler were killed in separate car crashes.
The 21-month-old girl died when she was hit by a car on Ardmore Walk in Tallaght, south Dublin, at approximately 5.30pm on Saturday.
She was taken to Tallaght Hospital where she was pronounced dead. The driver of the car was not injured.
In Sligo a 22-year-old driver and his 20-year-old front seat passenger were killed when their car crashed on the Ballyfarnan to Sligo Road at Sooey at approximately 11.40pm.
The rear seat passenger, aged 21, sustained serious injuries and is in a stable condition in Sligo General hospital.
Gardai said both roads are closed while Garda forensic collision investigators examine the scenes.