Local media identified the victims as being German holiday-makers, two men and a woman.
The blaze happened at Marina di Loano, a leisure port located near Finale Ligure on the stretch of coastline between Genoa and the French border.
Firefighters were called to the blaze around 6:00 am (0500 GMT). They were able to save one woman who had managed to get out and jump into the water, but the three others who were on the boat were trapped inside the cabin.
The AGI news agency described the woman who survived as being around 50. She was taken to hospital in a state of shock but otherwise not seriously injured, the agency said.
Several media said the woman who had died was the survivor’s sister. The two men were reportedly the respective partners of the women.
The ANSA news agency said on its website that the yacht was a 22-metre Maiora model sailing under a German flag and the name Southern Comfort. It had been moored at the marina for a year
