A 38-year-old man and a 39-year-old woman, both from the UK, were grievously injured in an accident that took place in Triq is-Salina.
The accident took place at around 11.15am, the police said.
The man and the woman were riding a quad bike that had impact with a Mini Cooper that was being driven by a 45-year-old man from Naxxar. The couple were taken to Mater Dei Hospital by ambulance. They were later certified as having suffered grievous injuries.
Police investigations are ongoing.