Italy's Culture Minister Francesco Rutelli wants a new anti-vandalism law after a man threw a bucket of red dye into the Trevi fountain in Rome.
The man, who fled the scene, left the baroque fountain spouting red water before technicians could shut off the water supply.
Leaflets left nearby denounced the cost of the RomeFilmFest, which has just opened in the Italian capital.
Officials said the fountain had not suffered permanent damage.
Engineers shut down the fountain to allow the red dye to drain away, before restoring a supply of clear water.
The Trevi, a baroque landmark dating from the18th Century, was popularised by films such as Federico Fellini's 1960 classic La Dolce Vita, in which Anita Ekberg frolics in its waters.
The protest leaflet was signed by an unknown group, ATM Azionefuturista 2007.
"You wanted just a red carpet - we want a city entirely in vermilion," it read, in an attack on the film festival's 15m-euro budget.
"We who are vulnerable, old, ill, students, workers, we come with vermilion to colour your greyness."
But Francesco Rutelli was unimpressed, calling the stunt "an unacceptable and irresponsible act of vandalism".