A British boy who disappeared in Spain six years ago when he was 11 has been found in a mountainous area in France, prosecutors said on Thursday.

The boy, Alex Batty, now 17, was found close to the town of Revel southeast of the southern city of Toulouse, regional prosecutors said.

"We have confirmed his identity and he will now return to Britain," Toulouse prosecutors said in a statement to AFP.

Greater Manchester Police in England said that the boy, who is from the northern English town of Oldham, had left the UK in September 2017 for a pre-agreed family holiday in Spain.

"This is a complex and long-running investigation, and we need to make further enquiries as well as putting appropriate safeguarding measures in place," Manchester police said.

The BBC said the boy's grandmother Susan Caruana had previously said she believed Alex's mother and grandfather had taken him to live with a spiritual community in Morocco to seek an alternative lifestyle without traditional education.

Alex Batty was last seen in Spain on October 8 of 2017, the day they were expected to return home.

The BBC said Alex Batty is currently in a centre for minors in Toulouse, awaiting the arrival of British police and consular staff to bring him back to England.

"The mother and grandfather, who do not have parental guardianship of Alex, have not been located but remain wanted in connection with his disappearance," the BBC said.

- 'His mother kidnapped him' -

His grandmother, who is divorced from the grandfather, told the Sun newspaper she was thrilled he had been found.

She said: "I am so happy. I have spoken to him and he is well.

"He is currently with the authorities in France. It is such a shock."

The La Depeche du Midi regional newspaper said he had been found by a student named Fabien Accidini after the youngster had been wandering for some four days in the mountainous area.

Accidini, who delivers medicines to pharmacies in the area, said it was raining hard when he picked up Alex Batty and he eventually told his story.

"He said that his mother had kidnapped him when he was around 12," the student told La Depeche.

"Since then, he had lived in Spain in a luxury house with around ten people. He would have arrived in France around 2021."

He had lived with his mother in a "spiritual community" in France and had "no animosity towards her but wanted to go back to his grandmother", said Accidini.

La Depeche said he had lived in France with his mother and grandfather in a "nomadic community" in the nearby Aude and Ariege departments.

There was no immediate information on the whereabouts of the mother and grandfather and what legal proceedings they may face.