Aid agencies are stepping up help following Saturday's devastating earthquake in Ecuador, amid concerns over the conditions faced by survivors.

Thousands of people were left homeless, making them vulnerable to dirty drinking water and disease.

The World Food Programme and Oxfam are sending supplies, while the UN said it was preparing a "major airlift".

The 7.8-magnitude earthquake left at least 480 people dead, more than 4,000 injured and 231 missing.

The cost of rebuilding is likely to be in the billions of dollars, President Rafael Correa said during a visit to the worst-affected region.

Six survivors were pulled from the rubble of a hotel near the town of Manta but despite the efforts of emergency teams hope is fading that others will be found.

The smell of rotting bodies is filling the air in the worst-hit areas, witnesses said.

From Tuesday, rescue efforts would become more of a hunt for corpses, Ecuador's Interior Minister Jose Serrano told Reuters.

Focus is turning to the survivors. The quake damaged communications, transport links and sanitation, hampering relief efforts.

Major international and aid organisations are sending help:

• The WFP is sending enough food to feed 8,000 of the most severely affected people
• The UN refugee agency (UNHCR) said it would send shelter and mosquito nets in an airlift due within 48 hours
• Oxfam said its first shipment of material providing safe drinking water would be sent on Wednesday
• Save the Children said it was working "around the clock" and trying to ensure children can continue their education despite the damage

Foreign nationals from Northern Ireland, Canada and the US have been confirmed among the dead and the death toll is likely to rise further.

"I fear that figure will go up because we keep on removing rubble," Mr Correa said in a televised address.

Reconstruction costs are likely to be huge at a time when the oil-producing country is already reeling from the slump in global crude prices.

Funerals for some of those killed have been held in Portoviejo and Pedernales, two towns that were the worst hit.

The US Geological Survey said the earthquake struck at a fairly shallow depth of 19.2km (11.9 miles), about 27km from Muisne in a sparsely populated area.

Scientists say there is no connection between the quake in Ecuador and a severe tremor in southern Japan, which also occurred on Saturday.