LONDON (CNN) — British counter-terrorism police arrested a man, who said he was a friend of a suspect in the Woolwich soldier killing, after he gave an interview to the BBC Friday night, the British broadcaster said.
The man, Abu Nusaybah, was arrested on suspected terrorism offenses after telling on air how his friend had been approached by Britain's domestic intelligence service, known as MI5, according to the broadcaster.
A BBC staffer, who did want to be named, told CNN that police were inside the BBC Broadcasting House building in central London waiting for the interview to conclude before they made the arrest.
Friends, acquaintances and British media identified 28-year-old Michael Adebolajo, a British national of Nigerian descent, as the suspect seen in a gory video from the scene of the Woolwich killing.
Authorities have not identified that individual or the 22-year-old man seized with him at the scene by armed police. Both suspects were shot and remain in hospital.
A Scotland Yard spokesman told CNN the arrest at the BBC was not connected to the murder investigation in Woolwich.
The brutal killing has sparked concerns that anti-Muslim sentiment may flare up in communities angered by the killing of the soldier, Drummer Lee Rigby.
Members of a far-right group, the English Defence League, called for Muslims to leave Britain as they rallied in Newcastle, northern England, on Saturday. The protest march came only hours after a group which monitors anti-Muslim abuse told CNN of a big spike in reported incidents in the past two days.
'Changed and withdrawn'
In the interview with BBC's Newsnight, Nusaybah said MI5 had approached Adebolajo in the past year, asking if he wanted to work for them.
Adebolajo rejected the approach, according to his friend.
Abu Nusaybah said the contact from MI5 occurred last year after Adebolajo returned from a visit to Kenya during which he was detained by security forces.
Adebolajo told his friend that he was physically assaulted and sexually threatened during his detention.
CNN is working to independently verify the allegations made by Abu Nusaybah about his friend's treatment in detention.
Abu Nusaybah went on to say that Adebolajo appeared changed and withdrawn after his return from Kenya.
The pair first met in 2002, he said. Abu Nusaybah had converted to Islam in late 2004 and Adebolajo followed suit about four months later, he said.
A security source told CNN that "we would never comment" on the kind of allegations made in the interview.
London's Metropolitan Police Service said a 31-year-old man had been arrested in London Friday night on terrorism-related offenses, but following standard practice would not give the arrested man's name.
Officers from Counter Terrorism Command arrested the man under the Terrorism Act, on suspicion of the commission, preparation or instigation of acts of terrorism. He was taken to a south London police station, where he remains in custody, a police statement said.
Search warrants were being executed at two residential addresses in east London, police said.
'Al Muhajiroun connections'
A self-proclaimed former radical associate of Abu Nusaybah told CNN Terrorism Analyst Paul Cruickshank he had been a follower of the group Al-Muhajiroun, a British group of Islamic extremists virulently opposed to UK intervention in Iraq and openly supportive of al Qaeda.
The former associate -- who spoke to CNN on condition of not being named -- spent time with Nusaybah in Al-Muhajiroun study groups in Luton, a town north of London, in the years leading up to the July 7, 2005 attacks on London's transit system, he said.
At the time, Adebolajo himself was a follower of the group and attended meetings in London, according to several Al-Muhajiroun insiders, before moving away from the group two or three years ago.
"Abu Nusaybah was very quiet, always smiling, and very religious," said his former friend, who has now shed his radical views.
He said their circle of friends in Luton included Taimour Abdulwahab al Abdaly, who carried out a suicide bombing in Stockholm in December 2010 in which he was the only fatality.
He said Abu Nusaybah had connections to a grouping of Somali extremists in Luton.
The brutal slaying of Rigby near the Royal Artillery Barracks in Woolwich, a working-class neighborhood in southeast London, shocked people across the United Kingdom.
One of the two suspects approached a man filming the gory scene in the Woolwich neighborhood and suggested that Rigby had been targeted only "because Muslims are dying daily" at the hands of British troops like him.
"We must fight them as they fight us. An eye for an eye and a tooth for a tooth," he said in the video aired by CNN affiliate ITN.
Britain's armed forces have served in Iraq and Afghanistan. All its combat troops are due to leave Afghanistan by the end of 2014.
It is understood that the two individuals suspected in the knife and cleaver attack were known to Britain's domestic security service. They had featured in previous investigations into other individuals, but were not themselves under surveillance.
CNN understands that one line of inquiry being examined in the Woolwich terror investigation is that suspect Adebolajo might have attempted -- but failed -- to travel to Somalia some time last year.
A third man, aged 29, who was arrested on suspicion of conspiracy to murder on Thursday in connection with the Woolwich investigation remains in custody.