Amnesty International is investigating a graphic video posted on the internet, which show men being beaten and tortured in Fiji.
The nine-minute video shows one man handcuffed in the back of a ute being beaten with rods, while another man is on the ground being tugged at by a dog.
The beatings are administered by men in plain clothes speaking Bauan - a Fijian dialect. It is thought the footage is from an incident last year where five prison escapers were apparently assaulted by the military when they were eventually recaptured.
Amnesty International executive director Grant Bayldon said a team in London was trying to verify the video.
"This appalling incident appears to be the latest example of abuse by the military. The Fijian authorities must treat this shocking footage with the utmost seriousness and immediately initiate an independent investigation," he said.
"Forced to undress and harassed by a dog, as men nearby laugh, it is difficult to watch," Mr Bayldon said.
"The subsequent brutal beating with batons is harrowing. It is torture."
Amnesty International is calling for an independent and transparent investigation into the video. Prime Minister John Key was expected to comment on the issue overnight from Mexico.
Human rights campaigner and lawyer Peter Williams, QC, said New Zealand aid could be withheld from Fiji if no charges were brought against the perpetrators of the alleged torture and beatings.
"I think we're waiting in New Zealand to see what the authorities are going to do about it. If no charges are brought then I think the New Zealand Government should bring some pressure on the dictatorship over there, the military Government, to do something about it."
The Fiji Police Force has confirmed it will investigate.