Guinea's military leader Capt Moussa Dadis Camara could be held responsible for the massacre of 157 protesters in in September, a report says.
The Human Rights Watch report says the killings were designed to silence opposition to military rule.
The authors say Guinea's presidential guard fired into the crowd until they ran out of bullets.
Capt Camara has previously blamed the deaths on "out of control" elements in the military.
The junta has said that 57 people died - and most of these were trampled underfoot, rather than shot.
The Human Rights Watch report says the military tried to cover up the massacre by removing bodies from hospital for secret mass burials. 
They say this was a crime against humanity, coming under the jurisdiction of the International Criminal Court.
The report names several military officers, including the current head of state, Capt Camara, who it says should be investigated further and face trial.
He is currently undergoing hospital treatment in Morocco after being shot by one of his aides.
The aide, Lt Toumba Diakite, on Wednesday said he had shot Capt Camara, because the military leader was trying to blame him for the massacre.
