Italian authorities say a Russian tourist has been fined 20,000 euros ($25,000) for engraving a big letter 'K' on a wall of the Colosseum, the latest act of vandalism by tourists at the ancient structure.

The news agency ANSA reported that the 42-year-old tourist was given a summary judgment Saturday of a fine and a suspended four-year jail sentence. He was spotted by a guard as he used a pointed stone to carve the 25-centimeter- (10-inch-) tall letter.

Union leaders, citing recent acts of vandalism, have complained about the lack of personnel to properly monitor Rome's archaeological treasures — with increasing numbers of visitors seeking to leave their trace on antiquity, causing incalculable damage.

It was the fifth incidence of vandalism by foreign tourists at the Colosseum this year.