The military moved to quell concerns over the safety of its nuclear facilities, including the main nuclear weapons research laboratory, close to the affected zone.
"I could say in a responsible manner that all these facilities are safe and secure," Ma Jian, a senior People's Liberation Army officer, told a news conference in Beijing. "There is no problem at all."
Offers of help have flooded in and rescue teams with sniffer dogs and specialised equipment from Japan, Russia, Taiwan, South Korea, the United States and Singapore are assisting. Donations from home and abroad have topped 6 billion yuan (434 million pounds).
Statistics from past earthquakes show some victims have survived up to nearly a fortnight under rubble.
Yet Fujiya Koji, head of the Japanese rescue team in Sichuan, conceded: "Generally by this stage the likelihood of survival is low. They say they have been finding some in Beichuan and we'll certainly keep trying."
HU VISITS
President Hu Jintao visited distraught families in Yinghua town and said he shared their pain. "We will try every effort to save your people once there is the slightest hope and possibility," he said, according to Xinhua.
In Beichuan, hard hit by the quake and which many people fled on Saturday following warnings a dam may collapse, worried relatives quarrelled with police who tried to prevent them entering the area, citing safety reasons.
"I've travelled all this way, and I don't know where my father is," said Chen Shiquan, who had come back from work in the neighbouring province of Qinghai to look for his father. "To let me get this far and then not let me in is too cruel."
At least three lakes, formed after rocks blocked a river, had burst their banks but caused no casualties. Officials were monitoring 21 cases where landslides had dammed rivers, Xinhua reported.
Dozens of schools collapsed in the area, crushing to death thousands of children taking classes at the time. Officials pulled out more bodies from the wreckage of the local primary school in Beichuan on Sunday. Forty-one corpses were laid out in front of the school.
A strong smell of ammonia and incense hung over the town, which was littered with massive boulders from a nearby mountain slope. All of the buildings in the town were either destroyed or appeared beyond repair.
China's Health Ministry said on Sunday there had been no disease outbreaks so far.
