Around 150 statues across Rome were wearing elasticated anti-pollution masks over their mouths on Thursday morning following a covert night-time operation by environmental activists.
Early-morning joggers and dog walkers alerted the police to the masks after finding them on statues of Roman emperors lining Via dei Fori Imperiali near the Colosseum, famous magistrates around Rome's Palace of Justice, and Garibaldi's mustachioed generals on the Janiculum Hill.
Statues in Piazza del Popolo and along two bridges across the River Tiber were also dressed in the protective gear.
The activists from environmental group Terra! had also hung no-entry road signs around the necks of the statues bearing the chemical symbol for carbon dioxide.
''It's incredible that they could have done this without anyone realising,'' said a dog walker who notified police to masks and signs placed over the white marble angels on the bridge leading to Castel Sant'Angelo.
''These angels are at least four meters high: even if it was during the night, you'd still need a ladder to reach their heads''.
Terra! said the masked statues were ''protesting together with activists'' about carbon dioxide emissions from cars and appealed to the European Commission to issue new regulations for the reduction of the greenhouse gas.
Restoration experts have long been concerned about the effects of air-borne pollutants on the city's statues and monuments.
Nitrates, heavy metals and sulphur dioxide - and not CO2 - are the main culprits for eroding and discolouring the marble and bronze masterpieces.
