The "unity events" were organised by London Citizens, a local community organising alliance, and included marches and handing out of leaflets with the message "Love London. No place for Hate".
"London doesn't just tolerate difference, it celebrates it, so it's great to see London Citizens' members rallying together to show that there is no place for division in our communities.
"I urge anyone affected by abusive behaviour to report it to the police immediately, and for Londoners to pull together and rally behind this great city now more than ever," said London mayor Sadiq Khan.
"As a Mayor for all Londoners, I take seriously my responsibility to defend the capital's fantastic diversity. I will operate a zero tolerance approach to any attempt to hurt and divide our communities, and I have asked the Met police (Scotland Yard) to be extra vigilant in tackling this deeply worrying rise in hate crime," Pakistan-origin Khan said.
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Meanwhile, a Muslim prayer event expected to draw more than 2,000 people in the beach town of Southampton has been cancelled because of rising racial tension.
"We have considered the political situation and unrest in the UK after the vote, the rise of racist activity and comments around other cities," a spokesperson said.