Règle correspondante
Practice Relating to Rule 29. Medical Transports
Section C. Respect for and protection of hospital ships
France’s LOAC Manual (2001) provides:
Convention II adopted in Geneva on 12 August 1949 protects hospital ships against armed attacks and capture. Considered as a hospital ship is a ship built or equipped specially and solely with a view to assisting the wounded. It must be the object of special marking, i.e. be painted white and covered with a red cross, so that its identification is possible. A hospital ship must not be equipped with weapons: it can, however, possess portable arms for self-defence. Ships chartered by a party to the conflict for the transport of medical equipment and lifeboats benefit from the same protections.
Furthermore, the warships of parties to a conflict can carry out support missions in the health domain; these ships are not considered as hospital ships. 
France, Manuel de droit des conflits armés, Ministère de la Défense, Direction des Affaires Juridiques, Sous-Direction du droit international humanitaire et du droit européen, Bureau du droit des conflits armés, 2001, p. 57.