Chinese Premier Wen Jiabao has described the earthquake in the southwestern province of Sichuan as the "most destructive" since China was founded in 1949.

"Saving lives is still our top priority as long as hope of survival still exists," the official Xinhua news agency quoted Mr Wen as saying.

But as those hopes fade, the Ministry of Health has issued a notice ordering bodies to be cleaned where they are found and buried as soon as possible, far from water sources and downwind from populated areas.

Mr Wen has been joined in the disaster zone by President Hu Jintao, who has been meeting survivors and encouraging rescue and relief workers.

The authorities say the death toll from Monday's earthquake is expected to pass 50,000 but say thousands of people have been rescued from the rubble of collapsed buildings.

Mr Wen urged survivors to ensure social stability as frustration and exhaustion grows among survivors, many of whom have lost everything and are living in makeshift tents or in the open air.

In small cities like Dujaingyan, tent towns are popping up on the outskirts as tens of thousands of refugees from this week's catastrophic earthquake pour into larger regional centres.

They have limited access to water, food and medicine, and there are concerns about the possible spread of disease.

Around 10,000 medical workers are working to sterilise water supplies, disinfect contaminated areas and are vaccinating people against disease.

Hospitals overwhelmed
Five days after the quake struck, few survivors are being pulled alive from collapsed buildings, but the massive rescue operation is continuing.

Hospitals are jam-packed with seriously injured patients.

China has mobilised 130,000 army and paramilitary troops to the disaster area, but the quake buckled roads and triggered mountain landslides, meaning that relief supplies and rescuers have struggled to reach the worst-hit areas.

Foreign aid accepted
After accepting help from Japan and Taiwan on Thursday, Beijing has now welcomed additional assistance in the form of rescue teams from South Korea, Singapore and Russia.

One Japanese rescue team is already on the ground in the provincial capital, Chengdu, and a second team was expected to arrive today.

Collapsed school 'broke regulations'
On Friday it also emerged a collapsed school in Beichuan County, where hundreds of children died, was built using cheap materials that could not withstand earthquakes.

Reporters say those responsible for building the school may face execution for ignoring official regulations.