Thousands of furious Venetians have marched in protest against large ships dubbed "sea monsters" clogging the city's narrow waterways and destroying the lives of locals.

An estimated 5000 people took to the docks near Venice's famous San Marco square to protest "bisons of the sea" dominating the lagoon city that is a UNESCO world heritage site.

Many carried banners reading "ships out of the lagoon" while others took to the canals in small vessels to demonstrate against the large boats they say wreak havoc on Venice's crumbling foundations.

Organisers No Grandi Navi said the march was designed to express outrage after an incident last week where 66,000 ton cruise ship, MSC Opera, smashed into a ferry and dock at San Basilio-Zattere in Venice's Giudecca Canal.


Social media footage showed people running while the 13-storey ship, with horns blaring, ploughed into the River Countess ferry. Four people were injured in the accident, and an investigation is determining what went wrong.

One protester known as Tommaso, said the lagoon has "never been so full" leaving the city and locals at the "mercy of mass tourism".

"We've been saying this for 6 years: these ships are too big! They pollute too much! These monsters poison us and have a terrible impact on the shores, on the foundations of our houses and monuments!" he said.

"On Sunday, the massacre was risked and we are here to say NEVER AGAIN! Our lives are much more important than your profits! This is why today we take back Piazza San Marco."

Venice has a permanent population of just 260,000 but is visited by up to 20 million people each year. Many of those arrive on large ships which critics say create waves that undermine the city's delicate foundations. Tourists also clog the narrow alleyways and increase the cost of services for locals. A climate change report from 2017 published in Quarternary International, claims that Venice could be permanently flooded by 2100.

Venice is not the only city cracking down on the tourist influx. Rome's populist mayor Virginia Raggi has introduced a crackdown on boorish behaviour with threats of expulsion for those caught bathing in Rome's fountains, climbing, eating, drinking of vandalising monuments.

"The Rome city centre is an area protected by UNESCO, so clearly our centre is our business ticket," Raggi told the Associated Press. She also promised "zero tolerance for those marring our city" with a penalty of being expelled for 48 hours.

Florence has also allowed local authorities to issue fines as high as EUR500 for eating on footpaths near famous landmarks. Other European cities such as Paris and Amsterdam are also considering measures to limit large crowds in tourist hots spots such as the red-light district and the Louvre.