PALERMO: One man died and six people were missing after a luxury yacht was struck by an unexpectedly violent storm and sank off the Sicilian capital Palermo on Monday, the Italian coast guard said.

The 56-metre-long (184ft) sailboat was identified as the British-registered Bayesian and sank with 22 people on board shortly before sunrise, the coast guard said in a statement.

The missing people were of British, American and Canadian nationality, the coast guard said. The 15 people rescued included a one-year-old child.

"The wind was very strong. Bad weather was expected, but not of this magnitude," a coast guard official in Palermo told Reuters.

Storms and heavy rainfall have swept down Italy in recent days with floods and landslides causing major damage in the north of the country, after weeks of scorching heat.

Eight of those rescued were transferred to local hospitals. All were in stable condition, local media reported.

The captain of a nearby boat told Reuters that when the storm hit he turned the engine on to keep control of the vessel and avoid a collision with the Bayesian.

"We managed to keep the ship in position and after the storm was over, we noticed that the ship behind us was gone," Karsten Borner told journalists.

He said that his crew then found some of the survivors on a life raft, including three who were seriously injured and took them on board before the coast guard picked them up.

Borner said "a little baby and the wife of the owner" were among the survivors, while the owner of the sunken ship and another child were among those missing.

The coast guard said the boat had been found at a depth of 49 metres and that divers were inspecting the wreck.

Prosecutors in the nearby town of Termini Imerese have opened an investigation to look into what had gone wrong.

A UK foreign ministry spokesperson said British officials were in contact with local authorities over the incident and were ready to provide consular support for Britons who were affected.