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.

Among those missing was British tech entrepreneur Mike Lynch, a person familiar with the rescue operation said.

The 56-metre-long (184-ft) 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.

The other boat "went flat on the water, and then down," he added.

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

Entrepreneur Lynch, aged 59, was acquitted in June by a jury in San Francisco of fraud charges linked to the sale of his software company, Autonomy, to Hewlett-Packard for $11 billion in 2011.

He said at the time that he was "elated" to be cleared in the criminal trial in which he denied any wrongdoing and blamed HP for botching the integration of the two companies.

DIVERS INSPECT WRECK

The coast guard said divers were inspecting the wreck, at a depth of 49 metres.

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

The Bayesian was built by Italian shipbuilder Perini in 2008 and was last refitted in 2020, and was managed by yachting company Camper & Nicholsons.

It won a string of awards for its design and can accommodate up to 12 guests in six suites and a crew of 10, according to online specialist yacht sites.

Formerly know as Salute, or health in Italian, its 75-metre mast is the tallest aluminium mast in the world, Perini said on its website.

The boat left the Sicilian port of Milazzo on Aug. 14 and was last tracked east of Palermo on Sunday evening, with a navigation status of "at anchor", according to vessel tracking app Vesselfinder.

A U.K. 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.