British counter-terrorism police on Saturday arrested three people suspected of involvement in the killing of a soldier hacked to death in a London street by two men shouting Islamist slogans.

The killing of the soldier in what the government said appeared to be a terrorist attack has led to angry protests against radical Islam and fears of a possible anti-Muslim backlash.

Abu Nusaybah, seen here during an interview with BBC, was arrested by British counter-terrorism officials on Friday. (Courtesy of the BBC)

Michael Adebolajo, 28 and Michael Adebowale, 22, are under armed guard in hospital after being shot and arrested by police on suspicion of murder on Wednesday.

The three men arrested on Saturday are suspected of conspiracy to murder. London police said two of them were hit by electric Taser guns, but neither needed hospital treatment.

Eight people have now been arrested in connection with the murder on Wednesday of 25-year-old Lee Rigby, who served in Afghanistan. No one has been charged.

Abu Nusaybah — a friend of Adebolajo — was arrested immediately after he gave a BBC Television interview Friday describing how Adebolajo may have become radicalized in Kenya.

Nusaybah also alleged that Britain's security services tried to recruit Adebolajo six months ago. Police said Nusaybah was wanted on suspicion of involvement in unspecified acts of terrorism.

Witnesses said Adebolajo and Adebowale 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.

Police have not officially named the two suspects — officials in Britain usually wait to name suspects until charges have been filed.

French police were investigating whether the stabbing of a soldier patrolling a business district west of Paris on Saturday was a copycat crime. The soldier was injured and his attacker fled.

French President Francois Hollande said the exact circumstances of the stabbing were still unclear, although police were "exploring all options."

"There are elements — the sudden violence of the attack — that could lead one to believe there might be a comparison with what happened in London," Interior Minister Manuel Valls told France 2 television. "But at this point, honestly, let us be prudent."

Attacks against mosques

Meanwhile, police on Saturday arrested three people on suspicion of posting racist comments on Twitter ahead of a march organized by the far-right group English Defense League in the northern city of Newcastle.

Some 2,000 members of the far-right English Defence League took to the streets of Newcastle on Saturday, calling for more action against radical Islam. (Neil Lancefield/Associated Press)

Newcastle police said up to 2,000 people took part in the demonstration. Protesters shouted "RIP Lee Rigby" and "Whose streets? Our streets."

The group, which has clashed violently with police in the past, has used Rigby's murder to criticize the British government for not paying enough attention to radical Islam in the country.

About 350 people from a local anti-fascist group staged a counter-demonstration. Police said both events passed off without major incident.

Faith Matters, a charity campaigning against extremism, said its helpline has received 162 calls since Rigby was killed from people reporting anti-Muslim incidents including attacks against mosques.

Questions for MI5

There have been questions over the role of the British security services in the months leading up to Rigby's killing.

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 domestic security service. However, neither man was thought to pose a serious threat.

Prime Minister David Cameron has said a parliamentary committee will investigate the security services' role.

In his BBC interview, Nusaybah said Adebolajo had been arrested and questioned in Kenya last year, and alleged he suffered physical and sexual abuse while in jail, afterwhich he became withdrawn.

"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.

This assertion was dismissed by the Kenyan government as a "fairy tale."

Nusaybah claimed that agents from Britain's domestic spy agency, MI5, approached Adebolajo after he returned to Britain and initially asked him if he had met specific Muslim militants, then asked Adebolajo if he was willing to act as an informer.

"He was explicit in that he refused to work for them," Nusaybah said. The BBC said he was arrested immediately after recording the interview.

It was not immediately possible to verify the information provided by Nusaybah, who said he had known Adebolajo for about a decade. MI5 does not publicly discuss its efforts to recruit informers.

MI5 Director-General Andrew Parker is expected to deliver a preliminary report next week to Parliament's Intelligence and Security Committee detailing what the agency knew about both suspects and whether MI5 could have done anything to stop the attack.

The directors of Britain's foreign spy agency, MI6, and Britain's eavesdropping agency, GCHQ, also are expected to give reports on what intelligence they had on the two men.

Converted in 2004

It is not uncommon, however, for special services officers to visit communities to ask people if they know potential terror suspects or others under MI5 surveillance.

Potential informants go through a screening process to determine if they should be trusted, what their motivation might be and whether their information would be likely to be accurate.

University investigation The University of Greenwich confirmed Saturday that records show Adebolajo was registered as a student there between 2003 and 2005. His academic progress was unsatisfactory and he did not complete his studies there, vice chancellor David Maguire said. The university did not have records for the second suspect, Adebowale. University officials are investigating whether there was any evidence of extremism on its campus, Maguire added.

Nusaybah said Adebolajo was converted to Islam around 2004. His account corroborates those provided by two Muslim hard-liners who said they also knew Adebolajo.

Anjem Choudary, a former leader of a banned British radical group called al-Muhajiroun, said Adebolajo was a Christian who converted to Islam around 2003. Choudary told The Associated Press that Adebolajo participated in several of the group's London demonstrations before Britain outlawed the group in 2010.

Omar Bakri Muhammad, another former al-Muhajiroun leader and radical Muslim preacher, said Adebolajo is a Nigerian who was born and raised in Britain. He said that Adebolajo attended his London lectures in the early 2000s, but added that he had not stayed in touch with the suspect since then.

"I don't know what Michael did since 2004 or 2005," Bakri told the AP. "Two years ago he stopped attending our open lectures and lessons as well as our activities."

Few details have emerged about Adebowale besides one reported brush with death as a teenager.

The Guardian reported Saturday that Adebowale was stabbed in 2008, when a man attacked him and two friends in a London apartment. One 18-year-old friend died and the attacker received a life sentence for murder, the newspaper said.