Italy's prime minister slams stunt as "vandalism, pure and simple".

Italian climate activists who threw vegetable soup over a Van Gogh painting at an exhibition in Rome on Friday risk hefty fines and up to five years in prison, according to news reports in Italy.

The Rome prosecutor's office has opened an investigation into the blitz by four members of the Ultima Generazione (Last Generation) movement who hurled pea soup at Van Gogh's The Sower on 4 November.

There was no damage caused to the 1888 painting which was protected by glass and was returned to the exhibition at Palazzo Bonaparte on Sunday after being assessed by experts from the Van Gogh Museum in Amsterdam who flew to Rome.

The moment climate activists in Rome throw vegetable soup over a Van Gogh masterpiece.pic.twitter.com/WKoKlNbwPJ— Wanted in Rome (@wantedinrome) November 4, 2022

The activists now face charges of "damaging, despoiling, vandalising, and the illicit use of cultural property", with penalties including jail sentences of between two and five years and fines of between €2,500 and €15,000.

The soup attack occurred at around lunchtime last Friday when four women in their twenties entered the museum separately, after buying entrance tickets, but without being permitted to bring backpacks or bags due to the security measures in place.

The activists - one from Rome and the other three from northern Italy - mingled with a group on a guided tour of the exhibition, reports state broadcaster RAI.

Once in front of the painting, they pulled out containers of vegetable soup hidden under their clothes and launched the contents onto the painting.

Rome motorists react furiously to the latest roadblock protest by climate activists today.pic.twitter.com/Z3JsnlDH6I— Wanted in Rome (@wantedinrome) November 2, 2022

The incident was harshly condemned by Italy's new culture minister Gennaro Sangiuliano as well as by the nation's far-right prime minister Giorgia Meloni who described it as "vandalism, pure and simple".

Ultima Generazione responded to Meloni's post on social media, reports RAI News: "We learn from Facebook that the Premier Giorgia Meloni is strongly outraged by a dirty glass in a museum and not by the effects of the climate collapse", adding: "Ours is not vandalism but the cry of alarm of desperate citizens."

The Van Gogh soup attack comes amid ongoing road blocks by climate activists during morning rush-hour traffic in locations around the Italian capital.

In August climate activists glued their hands to the base of the Laocoön sculpture at the Vatican Museums and in July they glued themselves to the protective glass covering Botticelli's Primavera painting at the Uffizi Galleries in Florence.

There was no damage caused to either masterpiece.