Anti-racist campaigners have warned that far-right groups will turn Saturday into a "day of hate" as up to 60 demonstrations are planned across the country over Drummer Lee Rigby's death.
Both the English Defence League (EDL) and British National Party (BNP) are planning events in towns and cities across the UK following the killing of the soldier in Woolwich, southeast London.
Hope not Hate has accused the groups of exploiting Rigby's death, with the EDL having already staged rallies in Woolwich, Newcastle and central London which escalated into violence and clashes with police.
Nick Lowles from Hope not Hate warned that the planned demonstrations could see the biggest far-right mobilisation in the UK in 30 years.
He said: "Towns and cities across England are going to have EDL events - many of them for the first time - and this is about the EDL taking their message of hate and division to communities across the country to try to stoke tensions and provoke a response."
The BNP's Nick Griffin had planned to stage a six-mile march from Woolwich to Lewisham in south London but the route has been changed to start in central London from Millbank to the Cenotaph in Whitehall because of police fears that the march could result in "serious disorder, serious damage to property, and/or serious disruption to the life of the community".
Commander Simon Letchford said: "The murder of Lee Rigby in Woolwich last week shocked our city. The right to protest is a fundamental part of our society, however, such a provocative mix of views being expressed in communities still hurting from Lee's murder could have resulted in ugly scenes on our streets."
The family of the young soldier have said that the 25-year-old would not have wanted anyone to carry out any attacks in his name.
His family said in a statement: "Lee loved life and he loved people. He had many friends from different walks of life - some with different religious beliefs and cultures. But this made no difference to Lee - he always treated others with the greatest of respect.
"We are struggling to come to terms with his loss of and we are truly grateful for everybody's support. We would like to emphasise that Lee would not want people to use his name as an excuse to carry out attacks against others."
Commanding officers of Rigby's regiment, 2nd Battalion The Royal Regiment of Fusiliers, has also urged its soldiers not to take place in any of the demonstrations. They described the marches as an excuse to exploit his death for "a range of self-serving and unhelpful reasons".
Regimental secretary Briga Ian Liles, of Fusiliers Association North East, said: "It is wrong and disgraceful that the death of one of our own should be exploited in this manner and that dishonour, by wrongful association, is brought on to the regiment.
"The reputation of the army will be damaged if individuals with visible connections to the army participate in demonstrations in support of Dmr Rigby that are associated with extremist organisations."
A spokesman for the Association of Chief Police Officers said: "Police are aware of a number of demonstrations planned. Forces across the country will be working closely with local communities as always to ensure these pass off with minimum disruption. While we will do all we can to facilitate peaceful protest, those taking part should be clear that the police will uphold the law."
The inquest into the death of Rigby has opened at Southwark Coroner's Court.
Michael Adebowale, 22, of Greenwich, has appeared before Westminster magistrates charged with his murder.
A second suspect, Michael Adebolajo, 28, remains under police guard in a London hospital and has not yet been spoken to by detectives.