Greta Thunberg effigy found hanging under Rome bridge

The teenage climate activist has been tipped as a possible winner of this year’s Nobel Peace Prize

Greta Thunberg speaks at a climate change rally and march in South Dakota on Monday. Reuters

An effigy of teenage climate activist Greta Thunberg strung up under a bridge in Rome has prompted Italian authorities to open an investigation for "aggravated threats”.

Images posted on social media on Monday showed an effigy with long braids with a sign written in English reading "Greta is your God".

Politicians condemned the stunt with Rome's mayor Virginia Raggi expressing the city's "solidarity" with Ms Thunberg and her family in a message on Twitter.

Leftist PD party leader Nicola Zingaretti criticised the "grisly violence" and said the party does not respect the values shared by those responsible for the effigy.

The 16-year-old Swedish activist hit international headlines after she launched a "Fridays For Future" campaign last year, calling for students across the globe to protest outside their parliaments to demand climate action.

Hundreds of thousands of school children and adults heeded Ms Thunberg's call last month in a global strike ahead of a climate summit at the United Nations General Assembly in New York.

The teenager then delivered an emotional speech to the General Assembly, chastising world leaders for their “betrayal” of young people around the world.

“You have stolen my dreams and my childhood with your empty words,” Ms Thunberg said.

She has been tipped as a possible winner of this year's Nobel Peace Prize.