WASHINGTON (AP) — The U.S. has transferred two Malaysian detainees at the Guantanamo Bay U.S. military prison to their home country, after they pleaded guilty to charges related to deadly 2002 bombings in Bali and agreed to testify against the alleged ringleader of that and other attacks, the Pentagon said Wednesday.

FILE - In this April 17, 2019, photo, reviewed by U.S. military officials, the control tower is seen through the razor wire inside the Camp VI detention facility in Guantanamo Bay Naval Base, Cuba. The U.S. has repatriated a Kenya man held for 17 years without charge at the U.S. military prison in Guantanamo Bay, Cuba. The move leaves 15 other men still waiting for release from Guantanamo after being cleared of wrongdoing after long detentions. (AP Photo/Alex Brandon, File)

Prosecutors say Mohammed Farik bin Amin and Mohammed Nazir bin Lep worked for years with Encep Nurjaman, known as Hambali, an Indonesian leader of al-Qaida affiliate Jemaah Islamiya. That includes helping Nurjaman escape capture after Oct. 12, 2002 bombings that killed 202 people at two night spots in Bali, U.S. officials said.

The two men entered guilty pleas to conspiracy and other charges in January. Their transfer comes after they provided testimony that prosecutors plan to use in the future against Nurjaman, the alleged mastermind, the Pentagon said in a statement.

Nurjaman is in custody in Guantanamo awaiting resumption of pre-trial hearings in January involving the Bali bombings and other attacks.

The two Malaysian men's transfers leave 27 detainees in custody at the U.S. naval base in Guantanamo Bay. President George W. Bush set up a military tribunal and prison after the Sept. 11, 2001 al-Qaida attacks on the U.S.

At peak, Guantanamo detained hundreds of men, most Muslim, in the U.S. military's “war on terror” after the Sept. 11 attacks.

Just two of the men at Guantanamo are serving sentences. U.S. prosecution of seven others currently facing charges has been slowed by legal obstacles — including those presented by the torture of the men in their first years under CIA custody — and logistical difficulties.

On Tuesday, U.S. authorities repatriated a Kenyan man, Mohammed Abdul Malik Bajabu, after 17 years at Guantanamo without charge.

His release leaves 15 other never-charged men awaiting release. The U.S. is searching for suitable and stable countries willing to take them. Many are from Yemen, a country split by war and dominated by an Iranian-allied militant group.

Amnesty International urged President Joe Biden to end the detention of those never-charged men before he leaves office. If not, the rights group said in a statement, “he will continue to bear responsibility for the abhorrent practice of indefinite detention without charge or trial by the U.S. government."