One person was killed and rescuers were searching for six others missing after a luxury superyacht sank off the coast of Italy's Sicily, officials said.

"This morning around 5:00 am (0300 GMT), following a violent storm, a 56-metre yacht called Bayesian, flying the British flag, sank near Porticello," the Italian coast guard said in a statement.

Rescuers backed by helicopter who were scouring the waters found one body on Monday, the coast guard said.

"One body was located in the wreck but not yet recovered, at a depth of around 50 metres," a spokesman told AFP.

Earlier, the coast guard said that four Britons, two Americans and one Canadian were missing, it said. It was not immediately known whose body was found.

The boat had 22 people aboard, including 10 crew members. Eight of those rescued were hospitalised.

The Bayesian was a luxury superyacht built by the Italian shipbuilding firm Perini Navi in 2008.

It had an 11.51-metre mast and could reach speeds of up to 15.5 knots, according to the Boat International website.