Bangui - At least 22 people including three staff members of medical charity Medecins Sans Frontieres were killed during a weekend attack by gunmen on a Central African hospital, a peacekeeper told AFP on Monday.Armed men from the ex-Seleka (rebel group) and of Fula ethnicity on Saturday afternoon attacked a hospital supported by MSF in the region of Nanga Boguila, killing at least 22 people, inc