A human rights group says mentally ill patients are suffering severe abuse at psychiatric hospitals in Ghana.

Human Rights Watch said Tuesday that many of those hospitalized are being chained to trees, and face physical and verbal abuse.

The rights group said abuses are even worse at centers known as "prayer camps," which operate without any government oversight.

Human Rights Watch said about 120 of the 135 residents at one camp were chained either to trees or to the walls inside cell-like rooms 24 hours a day, sometimes for months at a time.

Ghana's 2012 Mental Health Act went into effect in June and allows people with disabilities to challenge their detention in psychiatric hospitals. But the law does not apply to the prayer camps.