PARAMARIBO, SURINAME, DEC. 25 -- The armed forces appeared in firm control of this former Dutch colony today after toppling the nearly three-year-old elected government in an apparently bloodless coup.

Both the United States and the Netherlands, which provides $1.5 billion in annual aid to the multiracial nation of 400,000 in northeast South America, quickly denounced the military takeover and demanded that the elected leadership be returned to power.

"This action at a time when the entire hemisphere is moving toward democracy will only further isolate Suriname from the international community to the detriment of the Surinamese people," the State Department said.

The Monday night takeover apparently grew out of a festering dispute over government policies between President Ramsewak Shankar and Suriname's longtime military chief, Lt. Col. Desi Bouterse, who had resigned earlier in the day. It was led by Bouterse's deputy, Cmdr. Ivan Graanoogst, who told a national television audience that the military acted after the government had reneged on a promise to step down, and he promised free elections within 100 days. Graanoogst renewed that pledge today, declaring in a radio broadcast that "the army is not bent on having and keeping power."

Shankar, whose whereabouts were unclear for most of the day, said in a radio interview from his home this evening that the army had not curtailed his movements and that he was "free to go wherever" he wishes.

In 1980, Bouterse led a military coup that toppled the elected leadership of the Georgia-sized, mineral-rich country. He ruled until elections in November 1987 brought Shankar's Front for Democracy and Development to power.