Swedish teen climate activist Greta Thunberg turns 18

Sweden's Greta Thunberg, who pioneered a global climate change campaign as a 15-year-old, turned 18 on Sunday and promised to celebrate by exposing "dark secrets".

"Thank you so much for all the well wishes on my 18th birthday," Thunberg said on Twitter.

"Tonight you will find me down at the local pub exposing all the dark secrets behind the climate, school strike conspiracy and my evil handlers who can no longer control me. I am free at last."

Thunberg started a climate change campaign that swelled from a one-person school strike to a worldwide movement, drawing in millions of school children and adults.

She criticised world leaders over climate change in a speech to the UN in 2019, has clashed with US President Donald Trump, and last month called for urgent action five years after the Paris Accord.