More than a hundred people have been evacuated from the town, with the main roads closed to traffic and the electricity supply disrupted in the region.
"The number of victims due to yesterday's intense rain has risen to eight," emergency services said on Twitter.
Two British people died in a taxi caught in a flash flood.
The emergency services have been deployed to the area, with rescue personnel trying to assess the scale of damage via helicopters flying overhead, while residents were evacuated from rooftops and balconies.
INTENSE, damaging flash floods reported in Sant Llorenç, Mallorca (Balearic Islands, Spain) tonight, Oct 9! Report: Miguel Puigros Baldowski pic.twitter.com/VNHMKkkCp0— severe-weather.EU (@severeweatherEU) 10 октября 2018 г.
Shocking photos and videos of one of the worst floods on Majorca show cars floating away, and buildings being flooded with water.
Oh well another night in mallorca it is, very lucky indeed never seen rain like it try again tomorrow pic.twitter.com/DnPGsjOpcd— ian (@redian1973) 9 октября 2018 г.
— J.M.Vidal-Illanes 📚✍🏼 (@jmvidalillanes) 9 октября 2018 г.