Three Guantanamo Bay detainees hanged themselves with nooses made of sheets and clothes, the commander of the detention center said, bringing further condemnation of the isolated camp where hundreds of men have been held for years without charge.

Military officials said the suicides were coordinated acts of protests, but human rights activists and defense attorneys said the deaths signaled the desperation of many of the 460 detainees held on suspicion of links to Al Qaeda and the Taliban. Only 10 have been charged with crimes and there has been growing international pressure on the U.S. to close the prison.

Two men from Saudi Arabia and one from Yemen were found dead shortly after midnight Saturday in separate cells, said the Miami-based U.S. Southern Command, which has jurisdiction over the prison. Attempts were made to revive them, but they failed.

"They hung themselves with fabricated nooses made out of clothes and bed sheets," Navy Rear Adm. Harry Harris told reporters in a conference call from the U.S. base in southeastern Cuba.

"They have no regard for human life," he said. "Neither ours nor their own. I believe this was not an act of desperation but an act of asymmetric warfare against us."

To help prevent more suicides, guards will now give bed sheets to detainees only when they go to bed and remove them after they wake up in the morning, Harris said.

Gen. John Craddock, commander of the U.S. Southern Command, said in the conference call that the three had left suicide notes, but refused to disclose the contents.

One of the detainees was a mid- or high-level Al Qaeda operative, Harris said, while another had been captured in Afghanistan and participated in a riot at a prison there. The third belonged to a splinter group.

Some of the evidence against detainees is classified, so they are not permitted to know of it, and are thus unable to challenge it.

Saudi Arabia identified the two Saudi detainees Sunday as Mani bin Shaman bin Turki al Habradi and Yasser Talal Abdullah Yahya al Zahrani. The Saudi government has begun procedures to have their bodies sent home, Interior Ministry spokesman Mansour Turki said.

The military did not release the name of the detainees, and the identity of the Yemeni was not known.

"They're determined, intelligent, committed elements and they continue to do everything they can ... to become martyrs in the jihad," said Craddock.

He said all three had engaged in a hunger strike to protest their indefinite incarceration and had been force-fed before quitting the protest action. Military commanders said two were participating in the hunger strike as recently as last month, and described one of them as a long-term hunger striker who had begun the protest late last year and ended it in May.

Bush, who was spending the weekend at Camp David, expressed "serious concern" over the suicides and directed his administration to reach out diplomatically while it investigates, White House press secretary Tony Snow said Saturday evening.

Amnesty International said the apparent suicides "are the tragic results of years of arbitrary and indefinite detention" and called the prison "an indictment" of the Bush administration's human rights record.

Detainees "have this incredible level of despair that they will never get justice," said Barbara Olshansky of the Center for Constitutional Rights, which represents about 300 Guantanamo prisoners.

"I don't think this country wants the stain of injustice on it for many years to come," she said, appealing to the Bush administration "for immediate action to do the right thing."

Pentagon officials said the three men were in Camp 1, the highest security prison at Guantanamo, and none had tried to commit suicide before.

Though the military termed the deaths apparent suicides, the Naval Criminal Investigative Service was investigating to establish the official cause of death.

Saudi Arabia's state-sponsored Saudi Human Rights group blamed the U.S. for the deaths and suggested torture may have been involved.

"There are no independent monitors at the detention camp so it is easy to pin the crime on the prisoners ... it's possible they were tortured," Mufleh al-Qahtani, the group's deputy director, said in a statement to the local Al-Riyadh newspaper.

The U.S. has said it forbids the torture of detainees and has improved measures to prevent any mistreatment.

The commander of the Guantanamo detention center, Navy Rear Adm. Harry Harris, told reporters the three committed suicide by hanging themselves with "nooses made out of clothes and bed sheets."

Military officials said the men, all of whom left suicide notes, had been held in Guantanamo Bay for about four years. According to Harris, all three detainees had engaged in a hunger strike to protest their indefinite incarceration and had been force-fed before quitting their protest.

One of the detainees was accused by the US of being a mid- or high-level Al Qaeda operative, while another had been captured in Afghanistan and participated in a riot at a prison there, Harris said. The third belonged to a splinter group, he added.

Guantanamo officials have reported 41 unsuccessful suicide attempts by 25 detainees since the U.S. began taking prisoners to the base in January 2002. Defense lawyers contend the number of suicide attempts is higher.

Guantanamo Bay has become a sore subject between Bush and U.S. allies who otherwise are staunch supporters of his policies.

A U.N. panel said May 19 that holding detainees indefinitely at Guantanamo violated the world's ban on torture and the United States should close the detention center.

German Chancellor Angela Merkel, Danish Prime Minister Anders Fogh Rasmussen and British Prime Minister Tony Blair are among those who also recently have urged the United States to close the prison.

Until now, Guantanamo officials have said there have been 41 suicide attempts by 25 detainees and no deaths since the U.S. began taking prisoners to the base in January 2002. Defense lawyers contend the number of suicide attempts is higher.

Mark Denbeaux, a law professor at Seton Hall University in New Jersey who represents two Tunisians at Guantanamo, said he believes others there are candidates for suicide.

Denbeaux said one of his clients, Mohammed Abdul Rahman, appeared to be depressed and hardly spoke during a June 1 visit. Rahman was on a hunger strike at the time and was force-fed soon after, Denbeaux said.

"He told us he would rather die than stay in Guantanamo," the attorney said. "He doesn't believe he will ever get out of Guantanamo alive."