Two Britons are thought to have been killed during flash floods in Majorca.
He wrote on Instagram: "Our most honest condolences to the loved ones of the victims of the serious floods in Sant Llorenc".
A former mayor of the town of Arta near Sant Llorenc des Cardassar which was worst affected by the floods has also been named as one of the five fatalities.
A Foreign Office spokesman said: "We are supporting the family of two British people following their deaths in Spain, and will do all we can to assist them at this deeply hard time".
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At present, another 12 people have been reported missing on the island.
People walk along the damaged waterfront after a storm on the island of Mallorca, Spain, on October 10, 2018.
The two British victims, believed to be a couple, were reportedly in a taxi when they were caught in a flash flood.
Public broadcaster TVE showed footage of flooded streets and overturned cars along the guardrails of a major road. "We had to swim to try to survive".
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According to the Spanish media, people on the island have been rescued from rooftops and trees as 20cm (8in) of rain fell in four hours.
Officials have said more than 600 rescuers and medical staff were at work and that emergency relief centres had been set up in sports halls.
"My solidarity and support goes out to the families and friends of victims and all those affected by these tragic floods", Spanish Prime Minister Pedro Sanchez tweeted early on Wednesday.
Sanchez will be flying to the area later Wednesday, his office said.
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A minute's silence has been held by the Spanish parliament to remember the victims.