Update 2.40pm: Two 19-year-old men and a 21-year-old woman have been killed in a crash in Co Donegal.
Gardaí say excessive speed was a factor in the head-on two car collision that happened four miles outside Letterkenny, just before 1am this morning.
A 24-year-old man was also seriously injured in the crash.
Garda Inspector Michael Harrison believes the people in the two cars may have known each other, and he is appealing for information about what they were doing at the time.
He said: "These are somebody's children and we really need this information for the families, there are three devastated families in this county today.
"In total we've lost five in the last 24 hours, it has had a dreadful impact on this county, on the people of this county, to lose so many people to road traffic accidents."
Update 1.35pm: The bodies of two men and one woman, all aged in their 20s, have now been removed from the scene of last night’s fatal crash in Co Donegal.
The cars, as well as a truck which came on the scene, remain at the scene as a full forensic examination is carried out.
Meanwhile, Donegal County Council's road safety officer, Brian O'Donnell, urged people to be extra vigilant.
"This means always obey the speed limits, reduce speed in inclement weather conditions and allow plenty of time to arrive safely at your destination, always wear your seatbelt, never use a mobile phone while driving, and never drink and drive," he said.
The council said the latest tragedies were truly horrific and officials said thoughts and prayers were with the families and relatives of those involved.
"We as a community have had far too many tragedies, particularly road traffic collisions," the council said.
"No family should have to suffer the pain and loss of a loved one as a result of a road traffic collision. It should never be forgotten that behind every figure and statistic are real tragedies and real victims with real lives lost."
The council urged people to take personal responsibility for road safety.
"Road safety is not issue for the authorities alone. Each one of us who use our roads can make a difference and should take a moment to reflect on how we use the roads and whether or not we could improve our driving and ensure that we do not become another bleak statistic - or the cause of one. These recent tragedies have changed countless lives forever," it said.
Update 12.13pm: Garda Inspector Michael Harrison has said that three people who died in an overnight head-on collision between two cars may have known each other.
“A red Toyota Carina came into collision with a blue Peugeot 306,” he told Highland Radio.
“There was a lorry driver, he was driving over this road, and he came upon the scene , he was the first person that came upon the scene, and by all accounts what he witnessed was absolute carnage.
“The vehicles were travelling in opposite directions.
“Initially, it would appear that they may have known each other, but we need to get more information, and we have to get more information.”
Update 10.30am: CEO of the RSA Moyagh Murdock says the recent increase in fatalities on our roads is concerning.
“First of all, my condolences to the family and friends who have been devastated by this latest crash on our roads,” she said.
“In the past seven days, 10 people have been killed on the roads. Last night just highlights how vulnerable people are out there.
“We are seeing a significant increase [in the number of deaths] this year on the roads. It is up 16 on last year – 105 people killed so far this year.
“So really, we need a lot more work to try and reverse this trend.”
Three people have died in a two-car crash in Donegal.
Two men and one woman lost their lives in the collision just after 1am this morning in an area known as Corravaddy, around four miles from Letterkenny.
One man suffered serious injuries and is receiving treatment at Letterkenny Hospital.
The deceased remain at the scene this morning which has been sealed off for a forensic examination. The scene is currently closed to traffic and diversions are in place.
Garda forensic collision investigators have been requested to examine the scene and the local coroner has been notified.
Gardaí are appealing to anyone who witnessed the crash to come forward. Anyone with information is asked to contact Letterkenny Garda Station 074-9167100 or the Garda Confidential Line 1800 666 111.