The Ministry of Justice says the disturbance involved about 40 inmates at Maidstone Prison. It said in a statement that the incident "has been successfully resolved with no injuries to staff or prisoners."
Prison Officers Association vice chair Ralph Valerio told Sky News that the disturbance followed changes in conditions which mean prisoners have to spend more time in their cells.
The jail, some 50 kilometres southeast of London, houses about 600 prisoners, many of them sex offenders, and is a relatively low-security facility.