ECUADOR (AFP) - New aftershocks rattled Ecuador on Friday (April 22) as emergency workers continued searching for bodies after a devastating 7.8-magnitude earthquake that killed nearly 600 people.

A 6.0-magnitude quake struck just off the coast of northwest Ecuador around 10.00 pm Thursday (0300 GMT Friday), the US Geological Survey said.

It was followed by smaller aftershocks Friday morning, ranging in magnitude from 4.0 to 5.2, said Ecuador's Geophysics Institute.

AFP reporters in the region felt some shaking, but there were no immediate reports of new casualties or damage.

Ecuadoran authorities say more than 500 aftershocks have struck since Saturday's earthquake, the worst to hit Latin America and the Caribbean since the 2010 quake in Haiti, which killed between 200,000 and 250,000 people.

The official toll from Saturday's quake now stands at 588 dead and 130 missing.

Another 8,340 people were injured and more than 25,000 left homeless.

The United Nations appealed on Friday for US$72.7 million (S$98.5 million) to provide aid to 350,000 people over the next three months - about half the number it estimates are in need of help.

Humanitarian organizations warn the country still faces huge risks, as the legions of homeless are now prey to disease-bearing mosquitoes and dirty drinking water.

Electricity and water supplies are only being slowly restored.

Many businesses in affected areas have closed their shutters, fearing looters - which has made it all the more difficult to find food and basic necessities.

The quake crumpled hundreds of buildings up and down Ecuador's Pacific coast, turning picturesque resort towns into something resembling a war zone.

The smell of decomposing bodies has grown increasingly powerful in the tropical heat as workers continue searching for corpses in the ruins.

The disaster has also taken a heavy toll on Ecuador's economy, already struggling from the collapse in global oil prices.

President Rafael Correa announced a series of drastic economic measures in an address to the nation Wednesday night aimed at paying for what he estimates will be the US$3-billion cost of rebuilding - "two to three per cent of GDP," he said.

The measures include temporary income-tax increases equivalent to one day's salary a month, a one-year sales tax hike and a one-time levy on utilities. Ecuadorans with assets of more than $1 million will also have to fork over 0.9 percent of their wealth.

But even that will not be enough, according to the head of the national tax authority, who estimated the measures would bring in "$1 billion, maximum." Officials say 113 survivors have been rescued from the rubble.

But hopes of finding any more are slim.

In the port city of Manta, Andrea Figueroa, a young doctor who flew in from Mexico to help with the emergency response, had been scouring the ruins since Monday with her team, a rescue dog and a special scanner to detect vital signs in the rubble.

"There are no more survivors here," she said as they climbed around the remains of a hardware store.

Fire chief Eber Arroyo from the Ecuadoran capital Quito said the "operational threshold" of the rescue effort was over.

"At this point we are now managing decomposing bodies," he said.

The quake has left people traumatized, and the hundreds of aftershocks are only exacerbating it, said Catholic priest Ivan Onofre in Tasaste, near the devastated town of Pedernales.

"People are nervous, confused, expecting the worst, as if the most powerful (earthquake) had yet to hit. They have been affected psychologically," he said.

The quake came as a particularly severe blow to the tourism sector, just as the government was launching a major push to attract more tourists.

The South American country had only recently aired a Super Bowl commercial touting its beaches, islands and other charms - the first country ever to buy the American football championship's notoriously expensive ad airtime.

"We are worried about what comes next, how to rebuild and what to do so people can keep their jobs and prevent this from becoming a social crisis," said Jose Ochoa, head of the Ecuador Hotels Federation.