Two British men of Nigerian descent accused of hacking a soldier to death on a London street in revenge for wars in Muslim countries were known to security services, a source close to the investigation said on Thursday.

A woman who challenged knife-wielding assailants suspected of hacking to death a British soldier in London on Wednesday said she intervened because “it was better having them [the weapons] aimed on one person”.

Fears of a backlash against Muslims in Britain have intensified after dozens of Islamophobic incidents were reported in the wake of the grotesque murder of soldier Lee Rigby. The Tell Mama hotline for recording Islamophobic crimes detailed 38 incidents overnight on Wednesday, including attacks on three mosques. More were reported on Thursday.

Britain’s intelligence services came under pressure on Friday to explain how they let two Islamic extremists suspected of hacking a soldier to death in the streets of London slip through their net.

A Syrian-born Islamist cleric who taught one of the men accused of hacking to death an off-duty British soldier on a London street praised the attack for its "courage" and said Muslims would see it as a strike on a military target.

Police investigating the stabbing of a French soldier in Paris on Wednesday arrested a suspect sources described as a supporter of “radical Islam”.

Two prison officers have been injured in an attack at a British maximum security jail, officials said yesterday, with media reports claiming the assailants were Muslim inmates inspired by the brutal murder of a soldier.

French President Francois Hollande said the stabbing could not be linked to the London murder "at this stage", although Interior Minister Manuel Valls said the "sudden violence of the attack" was similar. The assault on Cordier three days after Afghanistan veteran drummer Lee Rigby was hacked to death on a London street in an Islamist attack will raise fears of a spiral of brazen violence against Western soldiers on their home soil.

For a movement that was on the verge of implosion less than a month ago, the English Defence League (EDL) has staged a major show of force in central London, signalling that the death of Drummer Lee Rigby has breathed new life into the far-right protest group.

The family of a man suspected of hacking a British soldier to death on a London street condemned the attack as senseless, distancing itself from the murder which has provoked an anti-Muslim backlash.

A meat cleaver is clasped in his blood-smeared left hand, the other - stained red with human blood too - waves manically as he shouts at the camera, ranting his justification for the atrocity on the streets of southeast London.

Michael Adebolajo, 28, has been charged with the murder of 25-year-old soldier Lee Rigby as well as the attempted murder of two police officers and possession of a firearm, London’s Metropolitan Police said

Britain is bracing not just for clashes with right-wing extremists but for possible copycat terror attacks after the brutal slaying of a young soldier on Wednesday. London's Metropolitan Police said more than 1,000 officers will be sent to potential trouble spots with armed response units. Only a fraction of Britain's police officers are armed.

In 2010, Michael Adebolajo was arrested with five others near Kenya’s border with Somalia, Kenya’s anti-terrorism police unit chief Boniface Mwaniki said. Police believed Adebolajo was going to work with Somali militant group al-Shabab.

British police said yesterday they were treating a blast outside a mosque in central England as a terrorist incident, saying nails were reportedly found at the scene. West Midlands police said they were alerted to reports of a loud bang in Tipton near Birmingham shortly after 1pm. No injuries were reported, but the immediate area was evacuated.

A battery of measures to prevent radicalisation of British Muslims was outlined by the home affairs minister, Theresa May. They included tougher pre-emptive censorship of internet sites, a lower threshold for banning extremist groups and renewed pressure on universities and mosques to reject so-called hate preachers.

Two men aged 28 an 24 were arrested at a home in southeast London, with police firing a Taser electric stun gun on the older suspect, and on a 21-year-old man they arrested in a street around 1.5 kilometres from the murder scene.

The chairman of an English mosque targeted by multiple petrol bombs has described the attack as attempted murder. The incident in Grimsby, in the eastern county of Lincolnshire, was the most serious attack on Muslims since the gruesome killing on a London street of British soldier Lee Rigby by two self-described Islamist extremists.

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.

Traces of DNA on an orange juice bottle and a surveillance video of a man praying in a mall have led to the arrest of a young suspect accused of stabbing a French soldier who was patrolling a crowded area just outside Paris.