A British couple are feared to be among six people who have died in flash flooding in Mallorca.

They were said to have drowned in a taxi as flood water engulfed the town of Sant Llorenç des Cardassar, about 40 miles east of the capital, Palma, on Tuesday evening.

A spokeswoman for the Balearic islands emergency services said two Britons were feared dead, but she could not say whether other British people were missing.

“A total of five people have died, including, it seems, two Britons,” she told the Guardian. Later, emergency services confirmed a sixth person had diedin S’Illot.

The spokeswoman added: “Two Spaniards and a Dutch woman also died. Two of them died in Sant Llorenç, one in Artà and two in S’Illot.”

She said the reported deaths of the two Britons had yet to be officially confirmed, adding that emergency services were not certain how many people were missing after the flooding. “We’re still gathering information,” she said.

The driver of the taxi is one of up to 15 people believed to be missing.

The Foreign Office said in a statement: “We are in contact with the Spanish authorities responding to flooding in Mallorca, and urgently seeking updates from them.”

There was heavy rain and flooding overnight in Sant Llorenç, emergency services said.

The regional government called an emergency meeting to coordinate rescue efforts and authorities said rescue workers and military units were heading to the area.

The Spanish prime minister, Pedro Sánchez, said: “My solidarity and support goes out to the families and friends of victims and all those affected by these tragic floods.”

Videos showed cars being washed away in fast-moving, muddy water more than a metre deep.

Officials confirmed five people had been killed and 300 rescue workers had been sent. Emergency relief centres were set up in sports halls.

Spanish weather forecasters said 20cm (8in) of rain fell in four hours. On Wednesday, Spain’s meteorological office, Aemet, issued orange alerts for heavy rain in three areas: the Balearic islands, parts of Catalonia and the Andalusian province of Málaga.

Aerial footage of the aftermath showed a road bridge near Palma was swept away in the floods.

The emergency services department put messages on Twitter in Spanish, Catalan, English and German, urging people to call 112 and let authorities know if they were stranded.

Rosario Sánchez, the Spanish government’s delegate to the Balearic islands, said: “It’s been a tough night but I think the day will be even tougher.”

Specialist rescue units from the Spanish army set off on a boat from Valencia, while a Spanish air force Hercules plane was due to take off at 5am local time (4am BST), carrying 90 rescuers. Two helicopters carrying three search dogs were also dispatched.

The prime minister was due to arrive in Mallorca early on Wednesday afternoon, a government spokeswoman said.

“The Spanish interior and territorial ministers and the government of the Balearic islands will present a report to the cabinet tomorrow to evaluate the loss of lives, the material damage done and to undertake the urgent, necessary measures in the face of the terrible suffered damage on the island of Mallorca,” she said.