Last year saw a number of riots in Argentine jails

The protest began nearly two weeks ago in a prison on the outskirts of the capital, Buenos Aires, and has since spread to more than 28 prisons.

Jail officials say striking inmates are all taking liquids and are regularly monitored for deteriorating health.

Complaints about the judicial system are frequent and many in pre-trial custody can wait years for a verdict.

Strike leaders say more than 80% of inmates are awaiting trial and are demanding that the legal system be speeded up. Some inmates are not scheduled to appear in court until 2013.

The strikers are also calling for better conditions. Official figures say the prison population has almost doubled in the past five years.

Prison conditions in Argentina, like most of Latin America, are generally poor, with overcrowding, poor food and corruption leading to frequent outbreaks of violence, and sometimes full-scale riots, the BBC's Daniel Schweimler reports from Buenos Aires.

Violence fears

The only prisoners not being asked to join the hunger strike are the elderly and those suffering from Aids and tuberculosis.

As well as faster trials, the prisoners are calling for the justice system to bring rules on the release of prisoners into line with recommendations by human rights groups.

Prison officials say they are in constant contact with the protesters and are holding a dialogue to reach some sort of agreement.

However, there is also concern about the possibility of violence between inmates participating in the protest and those who have decided not to.

"If the protest continues, there could be some incidents," said Buenos Aires provincial Justice Minister Eduardo Di Rocco.