A six-month old baby is in Wellington Hospital after suffering a severe head injury.

Police say an ambulance was called to a Kapiti address yesterday and the child was then airlifted to Wellington.

A spokesman says they're in the process of unravelling the circumstances that led to the injury.

Police have been speaking with family members who had contact with the child yesterday, and scene examinations are being carried out at properties in Waikanae and Raumati Beach.