Bodies washed up on beaches and fishermen reported bodies of people still tied to trees in a vain bid to stay safe from winds of 256kph and roaring seas.
Relatives sheltering in the port of Puerto Cabezas wept as soldiers in small boats carrying emergency food returned from tiny coastal villages and reported inhabitants missing.
Others rejoiced as boats brought bedraggled survivors to the port.
Miskito Indians hit
Felix mainly hit the turtle-fishing Miskitos Indians, who formed a British protectorate until the 19th century and still live in wooden shacks in isolated and sparsely populated.
About 35,000 of them live in Honduras and more than 100,000 in Nicaragua. The fierce storm struck fear into the local people.
"They told us a hurricane was coming and all the men and women were in their houses crying," said Ana Isolina Alvarado, an indigenous woman arriving from one of the tiny Cayos Miskitos islets in a fishing boat.
She took refuge from the storm in the boat after it got trapped in nearby mangroves.
Teams of Nicaraguan soldiers distributed food to cut-off villagers surviving on nothing but coconuts.
"We are still waiting for help," a Miskito woman called Lilian said from her coastal hamlet where 2,000 people stood helplessly in the debris of their wrecked homes.
Felix brought back memories of Hurricane Mitch, which killed 10,000 people in Central America in 1998.
This latest hurricane struck near Nicaragua's border with Honduras on Tuesday as a giant Category 5 storm, smashing up thousands of flimsy wooden shacks and flattening trees.