A 17-year-old German tourist was caught allegedly defacing the Colosseum in Rome on Saturday, the third reported act of vandalism against the World Heritage Site in recent weeks.

A teacher accompanied the student at the time of the incident, according to the Italian ANSA news agency.

The boy was stopped by the Italian domestic police, the Carabinieri, who were called in by the Colosseum's supervisory staff.

The teenager was "administratively sanctioned," ANSA said, without clarifying the type of sanction.

The scratch carved into the wall on the monument's ground floor damaged part of the brickwork, according to ANSA. 

Several acts of Colosseum vandalism

This is the third time in about a month that the Colosseum has been defaced by tourists, according to Italian officials. 

On Friday, a Swiss teen was filmed carving her first initial into the wall of the monument. She has since been identified by the police and is facing a sentence of several days' imprisonment and a fine of up to €15,000 (roughly $16,850).

Late last month, a British tourist from Bristol caused outrage after being caught engraving his and his girlfriend's names on the ancient walls. He apologized in a letter, claiming he was unaware of just how old the 1st century AD monument was.

The nearly-2000-year-old amphitheater is among Italy's most popular tourist attractions. Millions of tourists visit it annually.

rmt/lo (dpa, EFE)