A tense confrontation has developed at a prison in the Brazilian state of Sao Paulo where inmates are holding 17 people hostage and preventing hundreds of others from leaving.

The revolt began on Sunday during a visit by prisoners' relatives to the jail in the town of Sorocaba. At least one person has already been killed in the riot.

As our Brazil correspondent, Stephen Cviic reports, it is the latest in a series of disturbances which have swept through the country's prisons in the past few days.

Brazil's overcrowded jails are often the scene of disturbances and escape attempts but the Christmas period has been a particularly difficult time.

On Christmas Day nine inmates were killed after escaping from a prison near the north-eastern town of Fortaleza and on Monday morning one of the suspects from a notorious massacre in 1993 fled from a prison in Rio de Janeiro.

However most of the recent disturbances have taken place in the state of Sao Paulo.

The most serious of these in the town of Sorocaba is still going on.

It is not exactly clear what the 850 inmates want but they are reported to be armed with machine-guns and pistols and are holding 17 prison officials hostage.

Hundreds of their relatives are also inside the jail.

They were visiting when the rebellion started and it is possible some of them may be staying of their own free will.

Negotiations have been going on since Sunday evening but in an attempt to prevent a mass breakout the authorities are sending riot police to surround the prison.

The spate of rebellions in the past few days may have something to do with the unusually hot weather which Sao Paulo is experiencing.