Climate change activists turned the blue water of the Trevi Fountain in central Rome black with diluted charcoal on Sunday.

Around 10 activists from the climate group Ultima Generazione (Last Generation) entered the 18th century late-Baroque fountain holding a banner that said, "Let's not pay for fossil campaigns considering what is happening in Emilia Romagna," referring to the deadly flooding in northern Italy, which some experts have linked to the climate crisis.

"Our country is dying," other banners stated.

All activists were arrested and face vandalism charges, Rome police said.

Luisa Regimenti, councilor for personnel, urban security, local police and local authorities in the Lazio region, which includes Rome, condemned the act. In a written statement she said that it was the "umpteenth demonstrative act of eco-vandals" that hit "a symbol of Rome universally known in the world."

Calling it an "irresponsible blitz," she said dying the fountain was "a serious gesture, a worrying escalation that must be stopped with a safety plan for the monuments and the works of art most at risk in Rome and Lazio."

Rome Mayor Roberto Gualtieri tweeted: "Enough of these absurd attacks on our artistic heritage. Today the #FontanadiTrevi was smeared. Expensive and complex to restore, hoping there is no permanent damage. I invite activists to compete on a confrontational terrain without putting the monuments at risk."

He told local media on the scene that the 300,000 liter (66,000 gallon) fountain would have to be emptied and that the dyed water would have to be thrown away. "This will involve a significant intervention. It will cost time, effort and water."

This is the third time activists have put charcoal into famous fountains in the eternal city. In May, they dumped charcoal in the Fountain of Four Rivers in Piazza Navona and in April they targeted the Barcaccia fountain at the base of the Spanish Steps. The group has claimed responsibility in each incident.

"Charcoal in the water of the Trevi Fountain," they tweeted Sunday. "1 out of 4 houses in Italy is vulnerable to floods. How much longer do we have to wait for those in government to take concrete action?"

Some climate groups have criticized the Italian government for not being prepared for climate change in the wake of the flooding in northern Italy that killed at least 14 people and displaced more than 36,000.

The climate crisis "is affecting territories with increasingly intense extreme events, with risks to people's lives, and impacts on the environment and the economy. And Italy once again proves unprepared," said Italian environmentalist association Legambiente in a press release last Thursday

Legend states that anyone who throws a fountain into the coin will ensure their return to Rome. Each year around 1-1.5 million euros ($1.1-$1.6 million) in coins are collected for the Catholic charity Caritas. Around 3,000 euros ($3,200) a day are thrown into the fountain during busy tourist months, according to Rome's tourism board.