British police arrested a man under anti-terrorism laws at BBC headquarters after an interviewee said security services tried to recruit one of the 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 suspicion of the murder of 25-year-old Lee Rigby, a veteran of the Afghan war, three days ago.
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 conducted the interview, said police were waiting to arrest Nusaybah after the interview had finished on Friday. The pre-recorded interview was broadcast later that evening.
London's Metropolitan Police said counter-terrorism 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. He would not comment on the BBC interview.
A source close to the investigation told Reuters earlier this week that both men suspected to have attacked the soldier were known to Britain's MI5 internal security service. However, intelligence officers thought neither man posed a serious threat.
Prime Minister David Cameron has said a parliamentary committee will investigate the security services' role.
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 and questioned in Kenya. This assertion was dismissed by the Kenyan government as a "fairy tale".
"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 (interior ministry) spokesman said it never commented on security matters.
A Kenyan government spokesman said it had no record of Adebolajo ever visiting the east African country.
"We have never arrested him and we have never interrogated him, because if we had arrested him, we would never have let him go because of our experience of international terrorism," the spokesman said.
"Our conclusion is that this man is an imposter and a charlatan and wants to tarnish the image of our country."
Three days after the soldier's killing, police have yet to bring any charges. Police said Adebolajo and Adebowale are in a stable condition in hospital. The pair were in "no fit state" to be questioned by police, a government source was quoted as saying in the Times newspaper.
Witnesses said two men used a car to run down Rigby outside Woolwich Barracks in southeast London and then attacked him with a meat cleaver and knives, before being shot by police.
The pair told bystanders they were acting in revenge for British wars in Muslim countries.