84 of the 166 prisoners held at the U.S.-run Guantanamo Bay facility are now on hunger strike, U.S. military officials have said, according to BBC News.

The prisoners are protesting against their indefinite detention. Most are being held without charge.

Sixteen of the 84 prisoners are being force-fed and five are being treated in hospital. None has a life-threatening condition, according to the military.

The hunger strike started in February and has grown rapidly in recent weeks. The number of strikers reached 63 by last weekend.

Hunger strikes are frequent at Guantanamo, but the current protest - which began on February 6- is one of the longest and most widespread.

Guantanamo officials deny claims that the strike began after copies of the Koran were mishandled during searches of prisoners' cells.

Violence erupted at the prison on April 13 as the authorities moved inmates out of communal cellblocks where they had covered surveillance cameras and windows.

"We were trying to be patient and work with them and give them the opportunity to comply. We hit the point where... I felt we were accepting too much risk and it was time to take action," said Colonel John Bogdan.

Some prisoners used "improvised weapons" and were met with "less-than-lethal rounds", a military spokesman said, but no serious injuries were reported.

Nearly 100 of the detainees have reportedly been cleared for release but remain at the facility because of restrictions imposed by Congress and also concerns of possible mistreatment if they are sent back to their home countries.

"How can the military, even the military, hope to maintain discipline over a prison camp where there is absolutely no hope for those men confined here," said Lieutenant Commander Kevin Bogucki, a U.S. Navy military lawyer who was visiting his clients at the base.

The military detention centre opened in 2002 to hold suspects captured in counter-terrorism operations after the September 11, 2001 attacks in the U.S.