The bus was carrying around 30 people, when it fell about 20 metres into the yard of a private home in northwestern Rome, according to a Police dispatcher who said he was not authorised to release his name.
He said rescue workers had freed some of the tourists who were trapped in the mangled metal, and were transporting them to area hospitals.
The crash happened shortly after 11pm local time late on Monday.
The ANSA and Apcom news agencies cited witnesses as saying the tourists were Turkish, but that could not be confirmed.
The tourists' nationalities are not immediately known, but Rome police said they were not Italian.
No Australians killed
No Australians were involved in the accident according to the Department of Foreign Affairs and Trade (DFAT).
"We've had advice from Italian authorities and there were no
Australian citizens involved," a spokesman for DFAT said.