* Experts flag concerns after reviewing U.S. record
* Urge U.S. to limit use of killer drones abroad
* Back greater oversight of NSA surveillance
* Call for prosecution of Bush-era abductions, torture (Recasts with quotes from press conference)
By Stephanie Nebehay
GENEVA, March 27 (Reuters) - A U.N. human rights watchdog called on the Obama administration on Thursday to limit its use of drones targeting suspected al-Qaeda and Taliban militants and to curb U.S. surveillance activities at home and abroad.
U.S. drone strikes have led to excessive civilian casualties and unrestricted data collection has eroded the right to privacy, the U.N. Human Rights Committee said in its first report on Washington's rights record since 2006.
"A lot has to do with lack of transparency and oversight," Swiss lawyer Walter Kaelin, who is among the panel's 18 independent experts, told a news briefing where the findings were issued.
Referring to surveillance by the U.S. National Security Agency (NSA), Kaelin said: "What we are calling for is that if surveillance is undertaken, it has to be done in line with principles of legality, that there is the need for very clear detailed regulation containing safeguards for those under direct surveillance.
"We're calling also for a proportionate use of surveillance, not of everyone, but really limited to cases where such surveillance is necessary and justified."
The Obama administration on Thursday announced details of its plan to end the government's vast bulk collection of data from phone calls made in the United States, including new procedures to get judicial approval before asking companies for such records
"The announcement by President Obama is in line with our recommendation to adopt a law. I think our detailed recommendations provide some guidance on how such a law should be, what key elements should be included," Kaelin said.
The United States has obligations under a U.N. treaty on civil and political rights regarding those it puts under direct surveillance, even those outside U.S. territory, Kaelin said.
The panel 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, which were welcomed by U.S. activist groups.
"President Obama now has an opportunity to reverse course and reshape his human rights legacy by taking concrete actions like declassifying the Senate report on CIA torture, ending dragnet surveillance and unlawful targeted killings," said Jamil Dakwar of the American Civil Liberties Union (ACLU).
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 to rein in the missile 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, the panel's report said.
It should also "revisit its position regarding legal justifications for the use of deadly force through drone attacks," investigate any abuses and compensate victims' families, the committee said.
Kaelin said although the use of drones was not banned in armed conflict, the panel was concerned at the "very broad (U.S.) notion of the 'theatre of hostilities'."
"So it is really not about prohibiting but about limiting".
The committee called for more investigations into intelligence operations launched by the Bush administration in the wake of the Sept. 11 attacks.
Critics say the CIA's programme used harsh interrogation methods, including "waterboarding" or simulated drowning, that constituted torture banned by international law.
The report welcomed Obama's order in January 2009 to end the CIA programme, but noted only a limited number of investigations have been conducted 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". (Editing by Andrew Heavens and Sonya Hepinstall)