Whole villages were buried in mud, crops and property washed away, and roads and bridges destroyed. At least 7,000 people are believed to have died, but thousands more are unaccounted for.
"We have before us a panorama of death, desolation and ruin in all of the national territory," the Honduran President, Carlos Flores, said in a television address.
"There are corpses everywhere, victims of landslides or of the waters ... There are no undamaged zones or unharmed towns ... Bananas, coffee, water melons and basic grains are all lost. This is beyond pride or shame."
The hurricane brought 180mph winds in its wake and dumped two feet of water every day on the low plains and rolling hills of the two Central American countries. The water filled the crater of the Casitas volcano in north-western Nicaragua, causing it to disintegrate and spew mud and debris in waves over three or four villages.
One-third of the Honduran capital, Tegucigalpa, was reported to have been destroyed and the city's popular mayor, Cesar Castellanos, became a victim when his helicopter crashed while surveying the afflicted areas over the weekend.
Rescue workers, backed up by soldiers and emergency help from the United States army, described hearing women and children screaming for help as they sank into the mire.
After touring stricken zones, a shaken Nicaraguan Defence Minister, Pedro Joaquin Chamorro, said he had seen a pig nibbling at a child's corpse.
"It's hard to believe it unless you have seen it with your own eyes," Mr Chamorro said. US helicopters and transport aircraft were helping to pluck survivors off the roofs of houses left standing.
Meanwhile, the governments of the two countries, launched an appeal for food, medicines and water in an effort to stave off the risk of famine, epidemics and looting.
President Bill Clinton said the US would provide $2m (pounds 1.2m) in emergency aid, calling the disaster a "terrible tragedy". The British government has sent the Navy frigate HMS Sheffield to Honduras, and Navy personnel are on the ground helping to tend the injured.
The calamity appears to have superseded previous disasters to hit the region, including the 1972 earthquake that killed 5,000 people in the Nicaraguan capital, Managua, or the 1974 Hurricane Fifi, which claimed 2,000 lives in Honduras.
It could have untold economic and political effects on a region that has struggled to emerge from the US-sponsored wars of the 1980s. Nicaragua, in particular, was just getting back on its feet after a quarter-century of instability.
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