A mother and her three-year-old son were critically injured after a giraffe trampled them on a farm in South Africa on Tuesday, private medical firm ER24 has said.

Paramedics initiated "life support interventions" at the scene, before airlifting the two to hospital, ER24 said.

It is still unclear how the giraffe came to trample the woman, believed to be in her 30s, and her child on the farm in the remote northern Limpopo province.