Two French people working for an environmental organization in Madagascar have been killed, authorities said.

The French foreign ministry, in a statement late on Sunday, said they were killed "in an odious crime" on the small island of Sainte Marie, off the northeast coast of Madagascar.

Radio France International said the bodies of a young man and a young woman, aged 25 and 23, were found early on Sunday about 150 meters from a night club. Both had injuries to the head. They were volunteers for Cetamada, an environmental NGO that works for the protection of marine mammals.

French police will arrive on Monday to help the local police investigation, local authorities said.