Bainimarama said the emergency measures, which will be in place for a month, were needed to halt what he said were efforts by Qarase and members of his political party to "destabilise" the country.
"The lies they were spreading were not in the best interests of the nation"
Commodore Frank Bainimarama, Fiji's army chief
Under the emergency rules, the military has the right to detain people without charge.
"The lies they were spreading were not in the best interests of the nation," Bainimarama told the Fijilive Web site. "I have to tell them on behalf of the government and the military, we are not going to accept that."
Bainimarama has been under pressure from several neighbouring countries, as well as the European Union and the US, to return Fiji to democratic rule.
He has said elections will be held in March 2009, but critics say the handover must take place sooner.