The woman left in a critical condition after being assaulted in Co Tipperary has been named locally as Scarlett Faulkner.
She is a member of the Traveller community from Limerick city and is the mother of a six-year-old daughter.
Gardaí believe Ms Faulkner, who is aged in her 20s, was attacked by two people on the R494 at Birdhill near the M7 in Tipperary shortly before 5.30pm yesterday.
It is also believed that other people were present when the assault happened.
Ms Faulkner suffered severe head injuries and was airlifted to University Hospital Limerick, before later being transferred to Cork University Hospital.
Her condition has been described as critical.
Gardaí have conducted a technical examination of the scene and the road has reopened.
In a statement, gardaí said they "are seeking information on the movements of two vehicles, a grey 162 Ford Transit van and a blue 161 Volkswagen Touran people carrier".
They said the vehicles were "travelling in convoy or driving dangerously between 4.30pm and 5.30pm" in and around Birdhill village, the townlands of Cooleen, Crag Cross, Shower Cross, Kylebeg, Annaholty and Thornhill, all in Co Tipperary.
Gardaí have also said they are aware that video of the incident is circulating online and urged members of the public not to share such footage but instead provide it to them.
Ms Faulkner's family have been posting on social media about their devastation.
Her sister Victoria said her heart was "shattered" by what happened.
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Limerick Fianna Fáil TD and Minister of State Niall Collins urged witnesses to come forward.
"It's truly concerning and people are asking the question, what happened here," he said.
"How could such a brutal incident happen on a public road in the middle of the day," he added.
Mr Collins called the incident "truly shocking" and appealed "to anybody who has information to please contact the gardaí".
Gardaí are appealing for witnesses with information to come forward.
They are asking anybody who was driving on the R494 between Birdhill and the M7 between 5pm and 6pm yesterday evening to make camera footage, including dash cam footage, available.
