A cruise ship lost control as it was coming in to dock in Venice Sunday, crashing into the wharf and hitting a tourist boat, Italian media reported.
Tourists on land could be seen running away as the MSC Opera scraped along the dockside, its engine blaring, before knocking into the Michelangelo tourist boat, amateur video footage posted on Twitter showed.
Two people were lightly injured in the accident at San Basilio-Zattere in the Venice's Giudecca Canal, according to the media reports.
Another two were taken to hospital for check-ups. Their nationalities were not known, the reports said.
The crash may have happened after a cable used to link cruise ships to the tug boats that pull them into the city's canals broke, the Corriere della Sera daily said.
The Opera was then unable to stop because of the strong currents pulling it towards the dock, it said.
MSC Cruises, founded in Italy in 1960, is a global line registered in Switzerland and based in Geneva. The Opera, built 15 years ago, is registered in Panama and has a capacity for 2,679 passengers.