The UN has condemned an online video that appears to show two Fijian men being tortured by officials, calling on the Pacific nation's military government to bring the attackers to justice.

The army, which seized power in a 2006 coup, must launch an impartial investigation into the video, a spokesman for UN High Commissioner for Human Rights Navi Pillay said in a statement dated March 8 and released on Monday.

"We are shocked by the content of a video which has emerged over the past few days on social networks and the internet showing the apparent torture and inhuman and degrading treatment of two handcuffed men," he said.

"While the circumstances surrounding the video have not yet been ascertained, the acts being carried out in it are clearly illegal, and we condemn them in the strongest terms."

Graphic footage

The graphic footage posted on YouTube shows one handcuffed man being savagely beaten with batons and metal bars, and another being set upon by a dog as the animal's handler encourages it.

Fiji police have reportedly identified the attackers as security personnel, while Amnesty International, a UK-based human rights group, has said it suspects the footage was taken last year and shows prison escapees being abused.

Voreqe Bainimarama, Fiji's prime minister, said on Friday that he would stand by officers implicated in the video, arguing they were just doing their duty and "making sure we sleep peacefully at night".

Bainimarama has also dismissed concerns expressed by non-government organisations about the video, saying they "are paid by the international community to jump up and down every time we do something".

Bainimarama rules Fiji by decree and has curbed freedom of speech and assembly since taking power, as well as muzzling local media.

He has promised elections in 2014, but earlier this year introduced rules which effectively abolished most of the country's political parties and imposed restrictions on who can stand for office.