Those at risk include 11 foreign nationals sentenced in an unfair trial in November 2004 following the failed "coup plot" in which Britons Simon Mann and Sir Mark Thatcher were implicated. Dozens of Equatorial Guinean political detainees arrested in 2004 and held without charge or trial also face starvation.

According to information received by Amnesty International, in the last six weeks conditions at Black Beach have drastically deteriorated.

The provision of food by the authorities was reportedly reduced from a cup of rice daily in December 2004 to one or two bread rolls a day, and since the end of February 2005 provision of any prison food has been sporadic, with prisoners reportedly starving for up to six days at a time without any food.

Prisoners and detainees are now dependent on food handed to prison guards by families.

This means that the 11 foreign nationals and dozens of Equatorial Guinean political detainees arrested on the mainland are particularly at risk of starvation because they do not have families in Malabo to support them.

Many of those detained at Black Beach prison are already extremely weak because of the torture or ill-treatment they have suffered and because of chronic illnesses for which they have not received adequate medical treatment.

All those incarcerated are kept inside their cells 24-hours-a-day and the foreign nationals are also kept with their hands and legs cuffed at all times. The authorities have blocked all contact with families, lawyers and consular officials.

Amnesty International UK Campaigns Director Stephen Bowen said:

"Such near starvation, lack of medical attention and appalling prison conditions are nothing short of a slow, lingering death sentence for these prisoners.

"The authorities must provide food and medicine immediately and grant access to international monitors.

"Unless immediate action is taken, many of those detained at Black Beach prison will die."

In addition to the six Armenians and five South Africans convicted last November, Amnesty International has also learnt that four Nigerian nationals have been held in Black Beach prison for several months without charge or trial and without their embassy being notified.

Two former Black Beach prisoners are now being held at Malabo's central police station.

Convicted of attempting to overthrow the government in June 2002 after an unfair trial, Amnesty International considers them to be prisoners of conscience and is seriously concerned that they may now be tortured.

Amnesty International has issued an urgent alert to its members around the world, asking them to write to the authorities.

The organisation is calling on Equatorial Guinea to immediately provide:

• regular and adequate food
• medical care to all who need it
• remove any hand and leg cuffs
• end all incommunicado detention
• grant international humanitarian organisations such as the International Red Cross Committee immediate access to all those detained

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