A hunger strike at the prison camp at Guantánamo Bay, Cuba, has unsettled the facility's senior commanders and produced the most serious challenge yet to the military's effort to manage the detention of hundreds of terrorism suspects, lawyers and officials say.

As many as 200 prisoners -- more than a third of the camp -- have refused food in recent weeks to protest conditions and prolonged confinement without trial, according to the accounts of lawyers who represent them. Although military officials put the number of those participating at 105, they acknowledge that 20 of them, whose health and survival are being threatened, are being kept at the camp's hospital and fed through nasal tubes and sometimes given fluids intravenously.

The military authorities were so concerned about ending a previous strike this summer that they allowed the establishment of a six-member prisoners' grievance committee, lawyers said. The committee, a sharp departure from past practice in which camp authorities refused to cede any control or role to the detainees, was quickly ended, the lawyers say.

Officials said the prisoners usually accept the nasal tubes passively because they know they will be restrained and fed forcibly if necessary. Clive Stafford Smith, a British lawyer for several of the detainees, said an earlier hunger strike ended July 28 after the camp authorities agreed to improve conditions.