Tens of thousands of people are expected to take part in marches against racism and fascism on Saturday across the UK.
The demonstrations are organised by more 12 groups including Stand Up To Racism, Unite Against Fascism, the Muslim Council of Britain, and Stop the War.
There are parallel marches in capitals across Europe and around the world.
The activities are to commemorate UN Anti-Racism Day which commemorates the victims of the Sharpeville massacre in 1960, when 69 peaceful protestors against apartheid were killed by South African police.
Stand Up To Racism (SUR), the main UK organiser, said: "From Germany to Greece to Ferguson, people who want a society free from racism are saying no more. People are taking to the streets in large numbers to oppose the racist Pegida movement in Germany and the Neo-Nazi Golden Dawn in Greece, and to protest institutional racism and police violence against Black communities.
"People are outraged at the Islamophobic and anti-Semitic backlash after the Copenhagen and Paris attacks, and the mass media silence on the Chapel Hill shootings where three Muslim students were brutally shot dead, so many have mobilised under the slogan 'Muslim Lives Matter'. Immigrant communities are fed up with being wrongly blamed for an economic crisis they did not create. On UN Anti-racism Day people across the world will be taking a stand."
In London, protesters assembled in front of the British Broadcasting Corporation to march to Trafalgar Square, close to government buildings and the Houses of Parliament.
The protesters held banners reading "No to Islamophobia #MuslimLivesMatter", "From Ferguson to London #BlackLivesMatter", "Stamp Out Anti-Semitism" and "Immigrants Are Welcome Here."
Many organisations have warned of a recent escalation of hatred, racism, Islamophobia and anti-Semitism in the UK. "This racist tide will only be driven back by you and me standing up and confronting it," said a statement by SUR.
Diane Abbott MP, who planned to attend the London march, said: "A wave of ugly immigrant-bashing racism is sweeping through Britain, led by UKIP, pandered to by the media and conceded to by many others. This demonstration is the start of the fight back. We have to gather everyone willing to stand up to racism."
Maz Saleem, daughter of the late Mohammed Saleem will also attend. She spoke out about her father's death: "My father Mohammed Saleem was brutally murdered on the 29th April 2013 by a right-wing terrorist purely because he was a Muslim, not because he was Asian but because of his faith.
"Islamophobia is rife and Islamophobic attacks continue to rise fuelled by sensationalised headlines run by media and also by the governments stance on treating all Muslims as terrorists."
Some attendees at the London march posted images of a small counter-protest by members of the anti-Muslim group Britain First.
Last year, over 10,000 people from the UK, including students, trade unionists, migrants, and people from all faiths, took part in protests in London to call for action on racism.