There are unconfirmed reports that two Britons are among the casualties as the floods hit the Sant Llorenc area early on Wednesday morning.
The rain was so heavy a river burst its banks.
A spokeswoman with the regional emergency service said two British nationals and a Dutch woman were among the victims, but she couldn't confirm whether six more people were still missing at midday as local media reported.
The island was hit by devastating floods overnight, with torrential rainstorms hitting the town of Sant Lorrenc, about 40 miles east of the capital Palma.More news: Google unveils Home Hub
People walk along the damaged waterfront after a storm on the island of Mallorca, Spain, on October 10, 2018.
Hundreds of displaced residents are in emergency shelters, and around 80 soldiers are set to join more than 100 rescuers who are working in the area.
The weather agency, AEMET, said more heavy rainfall is expected Wednesday in eastern and southern parts of the Iberian peninsula.
Spanish authorities say that a total of five people have died, and a further 12 are missing.More news: Apple Watch Series 4 Crashing And Rebooting Due To Daylight Saving Bug
At least 220 millimetres of rain are believed to have fallen in the region, flooding homes, roads and fields.
The Spanish Prime Minister Pedro Sánchez tweeted: "My solidarity and support goes out to the families and friends of victims and all those affected by these tragic floods".
Sanchez was planning to travel to the area later on Wednesday, his office said.
A minute's silence has been held by the Spanish parliament to remember the victims. Streets in towns near Malaga on the Costa del Sol experienced flood water which was several feet deep.More news: China is the key to beating climate change
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