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LONDON (Reuters) - Britain’s interior minister Sajid Javid said social media firms must take action to stop extremism on their channels after Friday’s shootings at two mosques left at least 49 people dead.

Online accounts linked to the gun attacks had in recent days circulated white supremacist imagery and extreme right-wing messages celebrating violence against Muslims.

Facebook, Twitter and YouTube said they would take down content involving the mass shootings which were posted online as the attack unfolded.

“You really need to do more @YouTube @Google @facebook @Twitter to stop violent extremism being promoted on your platforms,” Javid wrote on Twitter. “Take some ownership. Enough is enough.”