While the full facts are not yet known, other inmates have alleged witnessing guards and police officers kicking and stomping on Burgess and beating him with night sticks in a sustained attack during the night of 16-17 March. They also claim inmates were allowed to join in at one point.

The allegations are deeply disturbing and suggest that Boggess may have been subjected to torture or other cruel, inhuman or degrading treatment in gross violation of international standards and treaties to which the US is a party. International standards require that whenever there is ground for believing that such treatment may have occurred, the authorities must proceed to a full, impartial inquiry.

Amnesty International is concerned by allegations that Boggess was sprayed with large quantities of mace or pepper spray, and that he may have been hogtied - a dangerous form of restraint which has been banned by many police departments.

The organisation welcomes reports that the FBI and state and local police have opened criminal investigations into the incident, and is urging that these investigations be conducted with the utmost thoroughness so that the full facts can be established and those responsible for any wrongdoing brought to justice.

Amnesty International is also calling on the state corrections department - which oversees jails - to conduct an inquiry into all the circumstances of what happened. Such an inquiry should include a review of what precipitated the incident; who was responsible for authorising or supervising the use of force; what quantities of chemical spray were used; and a review of the adequacy of jail policies and procedures on the use of force and restraints.

The organisation expressed shock at the allegations that guards and even inmates took part in a sustained beating - which, if confirmed, would suggest not only criminal wrongdoing but a serious breakdown in standards and supervision at the jail - and urged the authorities to make it clear that any use of excessive force and ill-treatment by guards will not be tolerated. It also called for international standards on the use of force to be incoporated into police guidelines and training.