A UK teenager found in France after disappearing in Spain six years ago when he was 11 is likely to return to Britain in days, police said Friday.

Alex Batty, originally from the northern English city of Oldham, was picked up by a driver in a mountainous area in southern France on Wednesday.

Police have said they suspect his mother and grandfather of abducting him in 2017 under the pretence of going on holiday in Spain, and then living in alternative lifestyle communes in Spain and subsequently the French Pyrenees.

"We're in close liaison with them (French authorities) and the Foreign and Commonwealth Office and our priority is to get him back to the UK and getting back to his family in Oldham as soon as possible," said Greater Manchester Police assistant chief constable Chris Sykes.

"I expect it to happen over the next few days."

Sykes added that Alex, who was discovered near Toulouse, had been found "safe and well".

His grandmother is his legal guardian, according to British media reporters.

"This is a huge moment for Alex, for his family, and for the community in Oldham.

"I can only imagine the emotions they've experienced as a family throughout this ordeal," the police officer said.

Sykes added that his force was "working around the clock with partner agencies and the French authorities to ensure they're all fully supported".

"We still have some work to do in establishing the full circumstances surrounding his disappearance and where he has been in all those years," he told reporters.

Sykes said that Alex had spoken to his grandmother on video call on Thursday night.

"Whilst she is content that this is indeed Alex, we obviously have further checks to do when he returns to the United Kingdom," he added.