Almost five million people have been left homeless by Monday's devastating earthquake in China's south-western Sichuan Province.
Chinese President Hu Jintao, visiting the province, said rescue work was at its most crucial phase.
Premier Wen Jiabao said the quake was the most destructive and widespread since the People's Republic was founded in 1949.
Its scale was greater than that of the Tangshan earthquake in 1976 which left 240,000 dead, he said.
China has announced an investigation into why so many schools have collapsed.
Further aftershocks - one measuring 5.9 - continued to strike the area, causing landslides that buried vehicles and knocked out communications only just restored.
Sichuan Vice-Governor Li Chengyun said 4.8 million people were now in "temporary shelter" following the earthquake. Local officials said the extent of homelessness in the region only became clear on Friday.