The Commonwealth Secretary-General, Don McKinnon, says he's very distressed by allegations the Fiji military has beaten people in custody.
He says the reports cast doubt on the military's motive for overthrowing the government.
Mr McKinnon says it is regretful that the Fiji military has always played a dominant role in politics.
The interim prime minister of Fiji, Commodore Frank Bainimarama, styles his takeover as a 'clean-up campaign' to wipe out corruption.
But Mr McKinnon says this purported motive is being undermined by the reported violence:
"Having a bloodless military coup is one thing, but when you hear reports about people getting beaten up, about people losing basic human rights as a result of this military rule, you have to be concerned about what is really being attempted here."
Mr McKinnon says the Fiji military is buoyed by its enormous contribution to UN peacekeeping - and because of this, it can get out of balance with the civilian government and government apparatus.