An Irish father lost three children in a fatal car crash in North Denmark, in which his wife and their newborn son survived.

Brian O’Shea and his wife Maria, were visiting her father. The family have lived in Pemberton in Western Australia for almost ten years. O'Shea owns a wood-heating business in Manjimup, while his wife, Dr O'Shea worked at Manjimup Medical Centre, the Irish Independent reports.

It is understood the Danish-born mother of the children was driving the car when it collided with another vehicle travelling in the opposite direction on Tuesday morning. The father was not in the car at the time.

The couple’s daughter Saoirse, 9, and two sons, Connor, 3, and Soren, 11, died as a result of the impact. The three children killed were niece and nephews of Irish celebrity chef Kevin Dundon.

Danish police said Dr O'Shea and her baby boy Torben were taken to hospital for medical treatment.

The car had been in the process of taking a left hand turn when it collided with an oncoming vehicle, close to the town of Sindal.

Police said the impact was severe as the other vehicle was travelling at 80 kilometres per hour.

"The mother was very shocked, but was not unconscious," a spokesman said.

"The other person in the other car was also shocked, but not hurt.

"It was a really bad accident. It was so awful up there for the witnesses."

A police investigation into the cause of the incident is ongoing.