LONDON - British police arrested a 10th suspect Monday in connection with the vicious street killing of a soldier in London, an apparent Islamic extremist attack that has horrified the country and heightened racial tensions.

The 50-year-old man was detained in Welling, east of London, on suspicion of conspiring to murder 25-year-old soldier Lee Rigby, Scotland Yard said. Police gave no further information about the suspect's identity.

The latest arrest came as more details trickled out about the background of Michael Adebolajo, 28, one of the two main British suspects in Wednesday's slaying. He and Michael Adebowale, 22, were shot and wounded by police at the scene.

Rigby, an off-duty soldier, was run over by a vehicle and repeatedly stabbed with meat cleavers Wednesday afternoon near his barracks in southeast London.

British officials said the two main suspects had been known to them for some time, but revelations that Adebolajo had been arrested in Kenya in 2010 - and claims that British security officials had tried to recruit him as an informer after that - have fueled questions about whether U.K. authorities could have done more to prevent last week's killing.

Adebolajo and Adebowale remain under armed guard in separate London hospitals. Four other men and the suspect arrested Monday remain in custody at a London police station, while one other man has been released on bail.

Rigby's killing and Adebolajo's apparent links to radical Islam have fed a spike in anti-Muslim sentiment in Britain, with police and activists reporting a surge in hate crimes, violence and vandalism.

Around 1,000 supporters of a far-right group marched through central London on Monday protesting the soldier's killing, clashing with a smaller group of anti-fascist demonstrators and scuffling with riot police. Police made three arrests.