Madagascan authorities have said they are treating the deaths of two young French volunteers as murder.

The man and the woman in their twenties were were found dead on the island of Sainte Marie, off the northeastern coast of Madagascar, on Sunday.

The island's mayor said both bodies showed signs of head trauma.

"They spent the evening in a nightclub and were found on the beach nearby," Mayor Bessaou Ismak Ado Crophe said.

"I saw the bodies. Both had injuries to the head."


Image: Sainte Marie is an island off the north-east coast of Madagascar

The pair had been volunteering in recent months at Cetamada, a local environmental non-profit organisation working to protect ocean mammals.

Madagascan Tourism Minister Roland Ratsiraka said an investigation has been launched into the deaths.

"The government strongly condemns this act and will ensure that the investigation will be transparent," he said.

In a statement, the French foreign ministry condemned the "odious crime that claimed the lives of two French nationals".

Cetamada's vice president, meanwhile, described the incident as "barbaric".

"I do not want to minimise this barbaric act, but we've been bringing dozens of volunteers here for 15 years and we've never had a problem this big," Jean-Jacques Ravello told news agency AFP.

He said fellow volunteers had gathered together following the incident and were "shocked psychologically".