NEW YORK — The U.S. military is holding about 500 juveniles suspected of being "unlawful enemy combatants" in detention centers in Iraq and has about 10 detained in Afghanistan, the United States has told the United Nations.

A total of 2,500 youths under the age of 18 have been detained, almost all in Iraq, for periods up to a year or more in President Bush's antiterrorism campaign since 2002, the United States reported last week to the U.N.'s Committee on the Rights of the Child.

Civil liberties groups such as the International Justice Network and the American Civil Liberties Union denounced the detentions as abhorrent, and a violation of U.S. treaty obligations.

In the periodic report to the United Nations on U.S. compliance with the Convention on the Rights of the Child, the United States confirmed that "as of April 2008, the United States held about 500 juveniles in Iraq."

"The juveniles that the United States has detained have been captured engaging in anti-coalition activity, such as planting Improvised Explosive Devices, operating as lookouts for insurgents, or actively engaged in fighting against U.S. and Coalition forces," the U.S. report said.

The majority are believed to be 16 or 17 years old.

The report said that of the total of 2,500 juveniles jailed since 2002, all but 100 had been picked up in Iraq. Of the remainder, most were swept up in Afghanistan.

"It's shocking to me that the U.S. government has not figured out a way to keep children out of adult prisons. It's outrageous, and it is not making us any safer, I can say that about Afghanistan from personal experience," Tina Foster, the executive director of the International Justice Network, said Sunday.