Police fired teargas at stone-throwing demonstrators in south-eastern Senegal Monday, injuring one person as protests erupted over the death of a deaf-mute youth in police custody, sources said.

A security source speaking on condition of anonymity said a man in his thirties had been arrested on Sunday night in the town of Kedougou during a "raid by paramilitary police while he was smoking cannabis". "After his arrest there were excesses which led to the youth's death," the source added, without giving more details on how he died.

"This morning the population revolted against the paramilitary police. During the protest another youth was injured." A resident of Kedougou told AFP that hundreds of angry residents had gone to the paramilitary police headquarters to demand punishment for those involved in the youth's death. 

They threw stones and police responded with teargas. About 500 people remained in front of the police offices by Monday afternoon, and businesses shut their doors fearing further violence.

An official from the paramilitary police said a "judicial and administrative investigation" into the death of the man had been opened, but that no other comment would be forthcoming at this stage.Human rights organisations including the local branch of Amnesty International demanded the "despicable crime" be investigated, in a statement published by the Senegalese Press Agency. 

Interior Minister Mbaye Ndiaye pledged action saying "an investigation has been launched... and there will be no cover-ups," as he appealed for calm.