The men are on the roof of a shed at Rye Hill prison near Rugby. The situation is peaceful and is being monitored, says the prison service.

Prisoner Steven Murphy phoned BBC Radio WM to describe what had happened. He said it was the second time prisoners had climbed on to the "aviary" roof.

"They're protesting at the way the prison's run," he told presenter Jon Gaunt on a live radio phone-in show.

Vulnerable inmates

HMP Rye Hill is situated in the village of Willoughby and is privately run by Group 4 Securitas. It opened in January, 2001.

It is a training prison holding 660 adult male Category B prisoners, who include 150 vulnerable inmates, housed in a purpose-designed Vulnerable Prisoner Unit, with its own regime and facilities.

The sentence requirement for HMP Rye Hill is more than four years with 18 months left to serve.