Mexico is charging three soldiers with homicide in the death of 22 suspected drug gang members who prosecutors allege were executed.

Attorney General Jesus Murillo Karam said late Tuesday the three are among eight who were arrested in connection with the June 30 shootout in Mexico state, 240 kilometers southwest of Mexico City.

The military initially said 22 suspects died in a prolonged gunfight that occurred when an eight-man patrol came under fire in the town of San Pedro Limon, an area known to be dominated by drug cartels.  

But Murillo Karam said the shootout lasted 10 minutes and afterwards the soldiers entered the warehouse and fired shots "that have no justification whatsoever."  Media reports have quoted witnesses as saying most of the 22 deaths happened after the suspects had surrendered.

Murillo Karam said five members of the eight-man squad appeared to have stayed outside while the killings occurred.
Rights groups have said the killings may prove to be one of the most serious massacres in Mexico in recent memory.

The United Nations has urged the deaths be investigated as possible summary executions.
More than 80,000 people have died in drug-related violence in Mexico since 2006, when then-president Felipe Calderon deployed the army to fight drug cartels.