Guards swept through communal cellblocks at the Guantanamo detention camp on Saturday and moved the prisoners into one-man cells in an attempt to end a hunger strike that began in February, a U.S. military spokesman said.
"Some detainees resisted with improvised weapons, and in response, four less-than-lethal rounds were fired. There were no serious injuries to guards or detainees," Navy Captain Robert Durand said in a news release.
He said the action was taken because detainees had covered windows and surveillance cameras to block the guards' view into the cellblocks.
"Round-the-clock monitoring is necessary to ensure security, order, and safety as detainees continued a prolonged hunger strike by refusing regular camp-provided meals," Durand said.
He said medical personnel had examined each detainee afterward.
The detention camp at the Guantanamo Bay U.S. Naval Base in Cuba holds 166 men, most of them captured more than a decade ago in counter-terrorism operations.
Saturday's early-morning sweep took place in Camp 6, a medium-security building where 80 to 100 detainees lived in cells that open into communal bays where they could eat, pray and watch television together. As part of the hunger strike, prisoners had been refusing to let food carts enter some of the bays.
Earlier in the week, Durand said 43 prisoners were taking part in a hunger strike, including 11 who were being force-fed liquid nutrients through tubes inserted into their noses and down to their stomachs.
The hunger strike began in February to protest the seizure of personal items from detainees' cells. Some prisoners told their lawyers that their Korans had been mistreated during the cell searches, which the U.S. military denied.
Attorneys, military officials and human rights monitors have all said the hunger strike was partly an expression of frustration over the prisoners' unresolved fate.
About half of them have been cleared for release or transfer, but Congress has made it increasingly difficult to move prisoners out of Guantanamo and President Barack Obama has failed to implement his 2009 order to shut down the detention camp.