AT least 13 prisoners have died of drug overdoses after inmates stormed a prison hospital in Venezuela during protests demanding better living conditions.

But activists questioned the official version and said the death toll could be far higher.

The disturbances at the David Viloria penitentiary began on Monday when a group of inmates went on a hunger strike seeking to force out the jail's new warden.

National Guardsmen were called in to restore calm and dozens of prisoners were transferred. The government said 145 inmates were being treated for intoxication.

The situation remains tense and prisoner rights activists expressed doubt about the government's version, calling for an investigation to discover why inmates would have voluntarily taken highly-toxic medicines.

Humberto Prado, co-ordinator of the Venezuelan Observatory of Prisons, said: "I don't think anyone is so stupid to ingest drugs just as a form of protest."