By Stephen Cviic BBC correspondent in Brazil

The authorities in the northern Brazilian state of Amazonas say 13 people have been killed in a prison rebellion.

The riot, which lasted 11 hours, started after the death of one of the inmates who his fellow prisoners said was beaten to death by guards.

Guns and knives were found in the jail, the authorities said, and they are linking the rebellion with the rapid growth of criminal factions all over Brazil.

They say the deaths of the inmates were the result of an internal dispute, but it is impossible to confirm this.

Prisoner 'tortured'

The rebellion began as breakfast was being served in the Anisio Jobin prison on the outskirts of the jungle city of Manaus.

It is not clear if the 400 inmates had any specific demands, but there is no doubt what the immediate cause of the riot was - the death on Friday of one of the prisoners.

Brutality, overcrowding and corruption are features of prison life

A medical examination of his body suggests he was tortured and beaten.

Twelve prisoners and one prison guard were killed during the rebellion.

Six prison guards who had been held hostage were eventually released unharmed, and by the time police shock troops went into the jail, the rebellion was over.

Organised crime

A state official linked the riot with the growth of a powerful organised crime syndicate, the First Command of the Capital (PCC) based in faraway Sao Paulo.

There is no doubt that Brazil's prisons have become havens of organised crime.

Last year, the PCC staged a series of simultaneous rebellions all over the country, and this year, Brazilians have got used to the unfamiliar sight of bomb attacks on public buildings, also blamed on the PCC.

On Thursday, the authorities in Sao Paulo carried out a blitz on the organisation, with 18 arrests and the closure of more than 30 telephone networks.

However, the problems in Brazilian jails are also the result of overcrowding, brutality, corruption among prison authorities and a slow justice system.