Lieutenant Commander Barbara Burfeind would not say how many underage youths were being held, how long they have been held at Guantanamo, or provide information on the circumstances that led to their detention in Afghanistan.

"The point is they are enemy combatants," she said. "Their age is really not a factor in their detention. They are detained at Guantanamo for a reason."

The United States has held detainees indefinitely without charges at Guantanamo since the end of the Afghan war and still has no formal legal process in place for deciding the status of the prisoners.

In Iraq by contrast, US military tribunals already have begun sorting through more than 6,850 prisoners and making decisions whether to release them or hold them as prisoners of war.

Burfeind said the underage youths who were sent to Guantanamo were originally assumed to be 16 years old.

It was unclear whether they were asked their age either in the initial interrogations or subsequently. She said they have been at Guantanamo for "at least several months."

Since they did not have birth certificates and proof of age was not available, the Armed Forces Institute of Pathology did tests that concluded they were under age, she said.

"There are a small number of individuals that are found to be under 16," Burfeind said.

She said that on the basis of those tests, they were removed from the population of adult detainees and put in a separate medium security facility at the base.

It was unclear when it was determined they were underage and how long them have been in their own facility.

"We recognize these are unfortunate circumstances that brought them here," she said. "The fact is that the use of children and juveniles in combat is a reality in many parts of the world."

Human Rights Watch voiced concern over the underage detainees and urged the United States to strictly observe inertnational children's rights standards.

"If these children have committed offences, they should be provided with counsel and adjudicated in accordance with standards of juvenile justice," said Jo Becker, childs rights advocacy director with the New York-based rights monitor.

"Otherwise they should be released immediately," Becker said.

Citing reports of as many as 25 suicide attempts at Guantanamo, Becker said children were at even higher risk "because of their relative isolation."

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