A man randomly attacked and beheaded a British woman in a supermarket on the Spanish resort island of Tenerife in the Canary Islands on Friday, officials said.

The suspect, believed to be a homeless Bulgarian man with a police record, was detained Friday by security guards after he ran out of the supermarket with the blood-soaked head in his hands.

A witness told broadcaster Cadena Ser that he saw the man drop the woman's head on the pavement after coming out of the store.

"I parked my car and saw a man running out with something bloody in his hands and a security guard chasing him. He threw it to the ground, it almost hit me and what he had been carrying was a woman's head," the unnamed witness said in a radio interview.

In London, Britain's Foreign Office confirmed the victim was a U.K. national, saying "we are now seeking further information."

Regional Interior Ministry delegate Dominica Fernandez said the suspect is believed to have entered the shop and stolen a knife, which he then used to assault and behead the woman, whose identity hasn't been released.

Fernandez told journalists the attack appeared to be random and that the man was well known in the area. It took place in the southern town of Arona, about 15 kilometres north of the beach resort of Los Cristianos.