BRISTOL, England (Reuters) - Greta Thunberg denounced politicians and the media on Friday for ignoring a looming climate cataclysm, saying that they were failing her generation with their inaction in the face of a world on fire.

Several thousand people attended a rally in the southwestern English city of Bristol to see Thunberg, the teenage activist who has reprimanded governments across the world over climate change.

Known simply as Greta, 17-year-old Thunberg has captured the imagination of many young people with impassioned demands for world leaders to take urgent action.

“I will not be silenced while the world is on fire - will you?” said Thunberg.

“This emergency is being completely ignored by the politicians, the media and those in power. Basically nothing is being done ... despite all the beautiful words.”

Supporters held placards reading: “Change the politics not the climate”, “The ocean is rising so are we!” and “At this point education is pointless.”

After she finished speaking, Thunberg led a march through central Bristol. Local police estimated that turnout was over 20,000 people.

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‘CHANGE IS COMING’

Thunberg rose to prominence when she starting missing lessons two years ago to protest outside the Swedish parliament building. Since then, she has become the world’s most prominent climate activist.

On Friday she marched behind a banner saying “Skolstrejk för klimatet” - or “school strike for climate” in her native Swedish.

Sacha Tomlinson, 14, missed school to attend the march.

“Greta’s really inspirational considering she’s so young. Even though she’s a child and a normal person she’s done so much to change (things),” he told Reuters.

“She’s given the generation confidence to stand up to people in government and power.”

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Thunberg has repeatedly upbraided world leaders including U.S. President Donald Trump for ignoring the perils of climate change, though Trump has dismissed what he calls the climate “prophets of doom”.

“We are being betrayed by those in power. They are failing us. But we will not back down,” Thunberg said at the rally.

“And if you feel threatened by that, then I have some very bad news for you. We will not be silenced, because we are the change, and change is coming whether you like it or not.”

Thunberg has been in Britain since last weekend. On Tuesday she visited the University of Oxford, where she met Malala Yousafzai, the 22-year-old Nobel Peace Prize winner and campaigner for girls’ education, who is studying there.

Thunberg called Yousafzai her role model, while Yousafzai said on Twitter: “She’s the only friend I’d skip school for.”