Fire engulfed a prison in the Chilean capital, Santiago, early today, killing more than 80 inmates and critically injuring 14 others, prison officials said.

The incident is the deadliest in the history of the country's prison system.

Officials said the fire was triggered during an early-morning fight between inmates in one of the crowded prison's five towers. Television footage showed part of the San Miguel prison in flames, with black smoke billowing from the building.

Relatives of the inmates gathered outside the prison, imploring police to let them in to help with rescue efforts.

Some threw rocks at police inside the prison perimeter, while others climbed on to the prison fence, their arms outstretched towards the burning building.

"Rusio Victor, wave a white T-shirt, Daddy," shouted seven-year-old Yadira Lopez, appealing to her father to signal that he was alive.

Luis Masferrer, the director of the national prison police, said: "This reflects the precarious state of Chile's prison system, which we have been denouncing and working to rectify since we took over [in March].

"Overcrowding is a factor that will have to be analysed in determining the causes of this terrible incident."

The justice minister, Felipe Bulnes, said the prison housed 1,960 inmates, nearly twice the 1,100 capacity.

The Bio Bio radio station reported that about 200 inmates were evacuated into a jail yard because of the fire.