The Fountain of the Lions in Piazza del Popolo in Rome was smeared with yellow and red paint.
The raid was carried out by two animal rights activists who also displayed a sign 'Enough animals in circuses'.
The police are on site.
The two activists were taken by the carabinieri to the San Lorenzo in Lucina barracks.
Their position is under investigation and they risk being sued.
The two would have thrown yellow, red and orange paint on the white marble of the base of the obelisk and above the lion statues.
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