More than 50 people were killed in three days of rioting in Tunisia's central Kasserine region, a union official told AFP Tuesday, reporting more violence and sniper fire overnight.

"The number killed has passed 50," said Sadok Mahmoudi, a member of the regional branch of the Tunisian General Union of Labour (UGTT), citing tolls issued by medical staff in the regional hospital in the town.

Security forces fired at demonstrators in clashes in various towns at the weekend, with the government saying they acted in self-defence and 14 people were killed.

The Paris-based International Federation for Human Rights (FIDH) said Tuesday at least 35 people were killed in the weekend unrest, while Amnesty International has estimated the toll at 23.

"It is chaos in Kasserine, after a night of violence, of sniper fire and pillaging," he said, alleging plainclothes' police were involved in looting businesses and homes.

A local official also said the situation was "chaotic" in the town, 290 kilometres (180 miles) south of the capital Tunis, describing sniper fire from roof tops and alleging police had shot at funeral processions.

A 75-year-old man and his wife were killed in the Ezzouhour area while they were going to bury their child on Tuesday, the official alleged, speaking on condition of anonymity.

Medical staff at the Kasserine hospital halted work for an hour on Tuesday to protest the high number of victims and seriousness of the wounds, he said.