One man has died and six people are missing after a luxury yacht sank in freak weather conditions off the coast of Sicily.

The 56m British-flagged Bayesian was carrying 22 people - 12 passengers and 10 crew - when a heavy storm that created waterspouts over the water struck early on Monday.

Fifteen people were rescued and a search operation for those unaccounted for - who include the British tech tycoon Mike Lynch - is ongoing.

Here is what we know about the tragedy so far, and how it unfolded.

The Bayesian was struck by a sudden and powerful storm in the early hours of Monday morning, witnesses say.

It was reportedly anchored to the sea bed outside the harbour at Porticello, a small fishing village to the east of Palermo, when what the Italian coastguard described as a "violent storm" hit.

The storm was so fierce that it caused waterspouts, or rotating columns of air and mist, to appear over the sea.

Witnesses told Italian news agency Ansa that the Bayesian’s anchor was down when the storm struck, causing the 72m (236ft) aluminium mast to break in half and the ship to lose its balance and sink.

It disappeared beneath the water at about 05:00 local time (04:00 BST).

Karsten Borner, captain of a nearby boat, said after the storm had passed, the crew noticed the yacht that had been behind them had disappeared.

"We saw a red flare, so my first mate and I went to the position, and we found this life raft drifting," he told Reuters.

His crew took on board some survivors, including three who were seriously injured.

Another witness, Fabio Cefalù, captain of a trawler, said he was about to go out on a fishing trip when he saw flashes of lightning so he stayed in the harbour.

"At about 4:15am we saw a flare in the sea," he said, according to the EVN news agency reports.

"We waited for this waterspout to pass. After 10 minutes we went out to the sea and we saw cushions and all the rest of the boat [that had sunk], and everything which was on the deck, at sea. However, we did not see any people in the sea.”

Another fisherman described seeing the yacht "sinking with my own eyes".

Speaking to the newspaper Giornale di Sicilia, the witness said he was at home when the tornado hit.

"Then I saw the boat, it had only one mast, it was very big," he said.

Shortly afterwards he went down to the Santa Nicolicchia bay in Porticello to get a better look at what was happening.

He added: "The boat was still floating, then all of a sudden it disappeared. I saw it sinking with my own eyes."

One of the survivors, British tourist Charlotte Golunski, told Italian newspaper La Repubblica how she held up her one-year-old daughter Sofia to stop her from drowning.

She said the two of them and her partner James survived only because they were up on deck when the yacht sank.

They were woken by “thunder, lightning and waves that made our boat dance”, and it felt like "the end of the world" before they were thrown into the water.

Charlotte said: "For two seconds I lost my daughter in the sea then quickly hugged her amid the fury of the waves."

She added: "I held her afloat with all my strength, my arms stretched upwards to keep her from drowning.

"It was all dark. In the water I couldn't keep my eyes open. I screamed for help but all I could hear around me was the screams of others."

There were 22 people on board when the storm hit, including 12 passengers and 10 crew.

One body has been recovered. It has not been formally identified, but the Palermo coastguard said it was the ship's cook. His nationality has not been confirmed.

Among the six people still missing is 59-year-old tech entrepreneur Mike Lynch, known by some as the "British Bill Gates".

Mr Lynch founded software giant Autonomy in 1996 and was made an OBE for services to enterprise in 2006.

In June, he was cleared of conducting a massive fraud relating to an 11 billion dollar (£8.64 billion) sale to US company Hewlett Packard.

Afterwards, he told the BBC in an interview he had been able to prove his innocence only because he had the wealth to pay the enormous legal fees required.

Sicily's civil protection agency also confirmed to the BBC that the missing include Mr Lynch's 18-year-old daughter Hannah, Morgan Stanley International bank chairman Jonathan Bloomer, and Clifford Chance lawyer Chris Morvillo.

La Repubblica reports that the six missing include four British nationals and two Americans.

Mr Lynch's wife Angela Bacares is among the 15 people to have been rescued, with eight of those receiving treatment in hospital, the Italian coastguard said.

Charlotte Golunski, her husband and daughter Sofia were also rescued and were unharmed, but taken to hospital for check-ups.

She said they had been on the yacht with a group of colleagues.

The daily Il Giornale di Sicilia newspaper reported the vessel had mostly British passengers on board, but also people from New Zealand, Sri Lanka, Ireland and British-French citizens.

A doctor based in Palermo said the "very tired" survivors were "constantly asking about the missing people".

Dr Domenico Cipolla told Reuters one woman he treated described the trip as a "corporate holiday", with some of those on board "very young".

"There were a lot of work colleagues, friends, a few husbands, wives, or a couple of friends who had joined in," he adds.

Six passengers remain missing and the Palermo coastguard says the search and rescue operation is continuing "incessantly".

Police divers have identified wreckage about 50 metres below the surface.

On Monday, four patrol boats, a helicopter and a team of divers were involved in the search. A naval and underwater team from the Palermo fire brigade also joined.

Footage from the wreckage site showed helicopters circling over several coastguard vessels as divers wearing bright orange descended into the water.

Francesco Venuto, a spokesperson for Sicily's civil protection agency, told the BBC on Monday rescue teams fear the bodies of those missing "must be" in the boat.

"We've been searching all day with helicopters and boats, we've found nothing. That wouldn't make sense, in this conditions we should have found something by now," he added.

On Monday, the UK's Marine Accident Investigation Branch sent a team of four investigators to carry out a preliminary assessment of the Bayesian's sinking, the BBC understands.

The director general of Sicily's civil protection agency, Salvatore Cocina, said the rescue operation would recommence at 06:30 local time (05:30 BST) on Tuesday.

A specialist caving search and rescue diving team arrived from Rome on Monday, hoping to "achieve results" either during the night or by Tuesday morning at the latest, he said.

A waterspout is similar to a tornado and can form over oceans, seas or large lakes.

The western half of the Mediterranean has experienced severe storms since the middle of last week.

Through Sunday night and into Monday morning, a clutch of bad weather passed by the north coast of Sicily.

BBC Weather forecaster Matt Taylor said: "A waterspout is a tornado that has occurred over water rather than land.

"They can form during intense storms, on the base of cumulonimbus/thunder clouds.

"Turbulence, and the wind blowing in slightly different directions around the cloud, can cause rotation under the base of the cloud and the spout to form.

"Like tornadoes, they bring powerful winds, but instead of picking up dust and debris they cause a water mist around the column of rotating air."

The superyacht can accommodate up to 12 guests in six suites, and is listed for rent for up to 195,000 euros (£166,000) a week.

She was built in 2008 by Italian company Perini Navi.

The Bayesian's registered owner is listed as Revtom Ltd, which is based on the Isle of Man.

The yacht's name is understood to derive from the Bayesian theory, which Mr Lynch's PhD thesis and the software that made his fortune was based on.

Mr Lynch's wife Ms Bacares is named as the sole legal owner of Revtom, which is registered in the Isle of Man.

The Bayesian completed a number of sailings in recent days, calling at various ports in Sicily, according to ship-tracking website VesselFinder.

A spokesperson for Camper and Nicholsons International, the firm that manages the 2008-built boat, told BBC Verify: "Our priority is assisting with the ongoing search and providing all necessary support to the rescued passengers and crew."