ROME, July 18 (Reuters) - Italy's antitrust authorities are going into combat over Rome's Colosseum, opening an investigation into ticketing operations that have seen tourists paying inflated prices to visit the ancient Roman arena where gladiators once fought. The antitrust authority said tickets were being bought "en masse through the use of automated purchasing systems". A ticket normally costs 18 euros ($20) but the official website on Tuesday showed there were just three places left until Aug. 7. Carlo Rienzi, the head of consumers rights body Codacons, said "secondary ticketing" was costing Italy millions of euros. "We ask the government to introduce new provisions capable not only of blocking secondary ticketing, but also of imposing very heavy penalties on those sites," Rienzi said in a statement.

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Persons: Carlo Rienzi, Codacons, Rienzi, Federica Urso, Elvira Pollina, Crispian Balmer, Angus MacSwan Organizations: Thomson