LONDON - Britain is bracing for clashes with right-wing activists and possible copycat terror attacks by Islamic extremists after the savage slaying of a young soldier, whose grieving family spoke Friday of their loss.

London police said more than 1,000 officers will be sent to potential trouble spots with armed response units. Most British police officers don't carry weapons.

Wednesday's attack was captured on video by passersby and made for gruesome viewing - one man is seen with his hands stained red with blood and holding two butcher's knives as he angrily complained about the British government and troops in foreign lands. A lifeless body is seen on the street behind him.

Analysts say the attackers wanted the publicity to inspire copycat attacks, and that they are already seeing an increase in chatter on extremist sites calling for such attacks.

"We can see the tempo being raised," said Maajid Nawaz, a former jihadist who is now with the London-based anti-extremist Quilliam Foundation.

Drummer Lee Rigby's anguished widow, Rebecca, said she never expected her husband to be in danger while in Britain: "You don't expect it to happen when he's in the UK. You think they're safe."