British police arrested a man under anti-terrorism laws at BBC headquarters after he said in an interview that security services tried to recruit one of two men arrested after a soldier was hacked to death in a London street.
Michael Adebolajo, 28 and Michael Adebowale, 22, are under armed guard in hospital after being shot and arrested by police on Wednesday on suspicion of murdering 25-year-old Lee Rigby, a veteran of the Afghan war.
A man identified by the BBC as Abu Nusaybah told its flagship news programme, Newsnight, that intelligence officers had approached Adebolajo six months ago to see if he would work for them as an informant. He said Adebolajo had refused.
BBC reporter Richard Watson, who interviewed him, said police were waiting to arrest Nusaybah after the interview had finished on Friday.
London's Metropolitan Police said counterterrorism officers had arrested a 31-year-old man on "suspicion of the commission, preparation or instigation of acts of terrorism".
A police spokesman said the arrest was made at the BBC building, but did not confirm the man's identity. He also said the arrest was not directly linked to the soldier's murder.
A source close to the investigation said earlier that both men suspected to have killed the soldier were known to Britain's MI5 internal security service.
In his BBC interview, Nusaybah alleged that intelligence officers visited Adebolajo's London home after the suspect made a trip to Kenya last year.
Nusaybah said his friend had been arrested in Kenya and then abused both physically and sexually while in jail there, after which his behaviour changed.
"Although that change wasn't necessarily one that became overt, aggressive or anything like that, he became … less talkative. He wasn't his bubbly self," Nusaybah told the BBC.
"He mentioned initially they [MI5] wanted to ask him if he knew certain individuals," Nusaybah told the BBC. "But after him saying that he didn't know these individuals, what he said was they asked him if he would be interested in working for them. He refused to work for them."
Asked about Nusaybah's comments, a Home Office spokesman said it never commented on security matters.
Kenya said it had no record of Adebolajo visiting the country.
"Our conclusion is that this man is an impostor and a charlatan and wants to tarnish the image of our country," a government spokesman said.
Three days after the soldier's killing, police had yet to bring any charges.
Additional reporting by Associated Press