China ramped up efforts on Saturday to stave off disease for millions of earthquake victims, as more miracle rescues amid the rubble offered hope in an increasingly desperate battle to save lives.

Five days after the enormous earthquake that the government estimates killed more than 50,000 people, there were rising concerns over potential disease outbreaks among the nearly five million survivors who have lost their homes.

Meanwhile, the death toll from the 7.9-magnitude quake continued to climb as authorities cleared their way through pulverised towns and gained better access to isolated areas -- gaining a better picture of the full scale of the horror.

The government raised the confirmed death toll by more than 6,000 to 28,881. But many expect the eventual figure could surpass even the government's estimate of over 50,000.

Entire towns in mountainous Sichuan province were flattened in Monday's quake, with the main zone of destruction spreading across 100,000 square kilometres (40,000 square miles) -- an area three times the size of Belgium.

The tremor, which could be felt as far away as Bangkok, saw mountainsides in Sichuan sheared off, roads split in two, and countless thousands of buildings toppled or in danger of collapse.

Since the quake, the most pressing priority has been to rescue those trapped amid the mass of twisted metal and concrete, and three more people, including a German tourist, were pulled out of the rubble on Saturday.

In Beichuan county, one of the worst-hit areas, a 69-year-old man was hauled out of the rubble after 119 hours, state-run Xinhua news agency reported, marking the longest time that a person is known to have survived in the debris.

Five hours earlier, 20 Chinese soldiers pulled out the German tourist from the wreckage of a building in a remote village that was just a few kilometres from the quake's epicentre, according to Xinhua, which did not identify him.

The miracle rescues on Saturday defied the warnings of experts that chances of survival were extremely small after 72 hours, and showed the determined statements from China's leaders and rescue workers had foundation.

"Giving up is excluded from our dictionary," the Xinhua quoted one rescue worker as saying.

Chinese Premier Wen Jiabao, who state media reported was personally leading rescue efforts, earlier said: "Where there is a beam of hope, we will spare no efforts to save the trapped."

China initially rebuffed offers of help from foreign rescue experts, but teams from Japan, Russia, Singapore and South Korea have now all begun operating in the disaster zone.

Teams have also headed in from Taiwan -- which China considers to be part of its territory -- and Hong Kong.

The international experts have brought in sniffer dogs, fibre-optic scopes, life detector systems and hydraulic cutters and spreaders.

As the rescue effort pressed on, other authorities focused on supplying fresh drinking water and improving sanitary conditions for the 4.8 million people who lost their homes and are living in tent cities or in the open.

Chian's health ministry said supplying clean water to the survivors was vital if the disease outbreaks were to be prevented.

Huge water purification machines capable of providing for up to 10,000 people a day were being taken into some of the most remote areas of Sichuan province, while authorities were frantically distributing portable toilets.

In Shifang city, where more than 2,500 people have been confirmed killed and thousands more remain missing, leaflets were being given to the shell-shocked, homeless survivors advising on hygiene and how to prevent disease.

In Dujiangyan city, hundreds of people living in tents had access to just one toilet.

"That toilet is too crowded, so maybe some people are going outside," said one woman who did not want her name to be used.

Amid the grief and shock, there was also increasing anger at how towns and cities could be felled in a matter of minutes.

The government said close to 7,000 schools -- a disproportionately high number of buildings -- were destroyed in Sichuan by the quake, which struck in the afternoon when many children were in class or taking their daily naps.

"Look at the building materials they used," said one resident in the rural community of Juyuan where the four-storey middle school was destroyed, blaming poor workmanship for the collapse.

"The cement wasn't mixed with water in the right proportion. There are not enough steel beams." Up to 900 children were killed at the school, while nearby buildings remained standing.