At the SXSW festival on Monday, the mayor of London, Sadiq Khan, asked Facebook and Twitter to do more to combat hate speech.

During his talk, Khan read hateful social-media posts about himself.

He suggested that tech companies should face fines if they don't remove hate speech quickly.

At the annual SXSW festival in Austin on Monday, the mayor of London, Sadiq Khan, made a moving plea for tech companies to take on hate speech.

During his talk, the mayor read racist tweets about himself.

"I say kill the mayor of London and you'll be rid of one Muslim terrorist," Khan read aloud. "I'd pay for someone to execute Sadiq Khan."

Khan, the first Muslim mayor of a Western capital city, said he read the half-dozen tweets or so not to "be portrayed as a victim" or "ask for sympathy," but to "illustrate that big tech has further to go in making the internet free of hate speech."

"But ask yourself this: What happens when young boys and girls from minority backgrounds see this kind of thing on their timelines or experience this themselves?" Khan said.

Khan said that tweets like the ones addressed to him send a message to these children that if they don't look a certain way or subscribe to the same establishment beliefs, they will grow up thinking there's no path for them in high-profile careers.

"We simply must do more to protect people online," Khan said.

Khan urged companies like Facebook and Twitter to show "a stronger duty of care" so that "social-media platforms can live up to their promises to connect, unify, and democratize the sharing of information and be places where everyone feels welcomed and valued."

The London mayor suggested that Facebook and Twitter remove offensive content and misinformation faster and face fines if they don't.

In January, Germany began enforcing a new rule that gives social-media platforms 24 hours to decide whether something is hate speech. German police are investigating a far-right politician, Beatrix von Storch, who described Muslims as "barbarians" on Facebook.

Khan says he expects Londoners to pressure their representatives to create a similar rule.

"This isn't about depriving people of free speech — this is about inciting hatred," Khan said. "This is about things that divide our community."