* Experts flag concerns after reviewing U.S. rights record
* Urge U.S. to review legal justification for drone use
* Call for prosecution of Bush-era abductions, torture (Adds details, quotes)
By Stephanie Nebehay
GENEVA, March 27 (Reuters) - A U.N. human rights watchdog called on the Obama administration on Thursday to review its use of drones to kill suspected al-Qaeda and Taliban militants abroad and reveal how it chose its targets.
In its first report on Washington's rights record since 2006, it also called for the prosecution of anyone who ordered or carried out killings, abductions and torture under a CIA programme at the time of President George W. Bush, and to keep a promise to close the detention facility at Guantanamo Bay.
U.S. officials did not immediately comment on the findings of the U.N. Human Rights Committee, which is made up of 18 independent experts.
The Obama administration increased the number of drone strikes after taking office in 2009 but attacks have dropped off in the last year. It has been under pressure from affected governments, the United Nations and activists to rein in the strikes and do more to protect civilians.
The United States should give more information on how it decided someone was enough of an "imminent threat" to be targeted in covert operations in Pakistan, Afghanistan, Yemen and Somalia and other countries, the report said.
It should "revisit its position regarding legal justifications for the use of deadly force through drone attacks," investigate any abuses and compensate victims' families, the committee added in its conclusions.
"MEAGRE NUMBER OF CRIMINAL CHARGES"
The committee also called for more investigations into intelligence operations launched by the administration of President George W. Bush in the wake of the Sept. 11 2001 attacks on America.
Critics say the CIA programme used harsh interrogation methods, including "waterboarding" or simulated drowning, that constituted torture banned by international law.
There has only been a limited number of investigations into "unlawful killings ... and the use of torture or cruel, inhuman or degrading treatment or punishment of detainees in U.S. custody, including outside its territory, as part of the so-called 'enhanced interrogation techniques' programme," it said.
The report welcomed Obama's order in January 2009 to end the CIA programme.
But it noted with concern that all reported investigations into alleged abuses were closed in 2012 "leading only to a meagre number of criminal charges brought against low-level operatives."
The panel said many details of the CIA programme remained secret, hindering accountability and redress for victims.
In an apparent reference to lawyers who drew up memos justifying the Bush-era interrogation techniques, it said: "The responsibility of those who provided legal pretexts for manifestly illegal behaviour should also be established."
DEATH PENALTY, DETENTIONS
The U.N. experts also voiced concern at the U.S. use of the death penalty and in particular "racial disparities in its imposition that affects disproportionately African Americans".
They regretted mandatory detention of immigrants for prolonged periods of time, deportations of immigrants and the "exclusion of millions of undocumented immigrants and their children from coverage under the Affordable Care Act".
The 18 experts examined U.S. compliance with a landmark treaty on civil and political rights at a two-day session earlier this month.
Washington says the pact does not apply to U.S. extraterritorial operations, facilities or officials holding suspects abroad in the context of the U.S.-led "war on terror".
The U.N. committee again urged the United States to interpret the treaty "in good faith" and acknowledge that it applied to U.S. operations and personnel abroad.
"It is not just the committee position and the World Court position, it is the position of very many states," chairman Nigel Rodley, a British law professor, told the March 14 talks. (Reporting by Stephanie Nebehay; Editing by Andrew Heavens)