Swedish climate activist Greta Thunberg hit back at Donald Trump on Twitter late on Thursday saying the US president should "chill" about the election, a repost to his tweet last year mocking the teenager over what he called her anger management issues.

Commenting on Trump tweeting "STOP THE COUNT!" on Thursday, as the election race in the United States went to the wire, 17-year-old Thunberg tweeted: "So ridiculous. Donald must work on his Anger Management problem, then go to a good old fashioned movie with a friend! Chill Donald, Chill!"