KAMPALA, Dec 21 (Reuters) - The deputy leader of Uganda's Lord's Resistance Army rebels, Vincent Otti, begged for his life when his boss Joseph Kony had him killed after tricking him into visiting his home, a BBC report said on Friday.

Referring to a "diplomatic briefing" collating eyewitness testimony, the World Service radio and its sister Web site said details had emerged of the alleged killing of the former rebel commander.

But a diplomat closely involved in peace talks said he doubted the testimony, which he thought came from LRA defectors with their own interests who fled months ago.

Numerous LRA deserters have said that Kony, whose 20-year rebellion killed tens of thousands of people and uprooted 2 million before a ceasefire last year, shot dead his number two, accusing him of spying.

The reports cast a dark cloud over peace talks as Otti was seen as a prime mover behind the LRA's decision to negotiate.

The BBC story, which did not cite any part of the document it described as confidential, said Otti was called to Kony's hideout in northeast Democratic Republic of Congo.

"Mr Otti arrived ... to find it surrounded by the leader's personal guards," it said. "Sensing something was wrong, Mr Otti phoned his boss, but was reassured all was well."

A guard then aimed a pistol at him and told him he was under arrest. Stripped of his shirt, bound and blindfolded, he cried, asking what he had done wrong. He then begged for his life but was shot dead.

A diplomat to the talks, who declined to be named, said he thought the account came from LRA defector Sunday Otto, who told a less detailed story to journalists in November.

"I'm not aware of any diplomatic briefing. This sounds like old testimony from defectors like Captain Sunday. It may be true but you have to take into account they have reasons to lie. Captain Sunday is particularly prone to lying," he said.

He added: "It's highly likely Otti's no longer there but it's all speculation, you have to keep room for doubt." (Reporting by Tim Cocks, editing by Tim Pearce)

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