Images posted on social media showed an effigy with long braids with a sign written in English reading “Greta is your God”.
Politicians slammed the stunt with Rome's mayor Virginia Raggi expressing the city's “solidarity” with the Thunberg family in a message on Twitter.
Vergognoso il manichino di @GretaThunberg ritrovato appeso a un ponte nella nostra città. A lei e alla sua famiglia la mia solidarietà e quella di tutta @Roma. Il nostro impegno sul clima non si ferma. pic.twitter.com/YXMXMJDA3D
— Virginia Raggi (@virginiaraggi) October 7, 2019
Leftist PD party leader Nicola Zingaretti condemned 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.
OPINION: Why Italy should listen to Greta Thunberg
Hundreds of thousands of school children and adults heeded Thunberg's call last month in a global strike ahead of a UN climate summit.
She has been tipped as a possible winner of this year's Nobel Peace Prize.