Between 3,000 and 5,000 people may have been killed by an earthquake measuring 7.8 in just one county of south-western China's Sichuan province, reports say.
Some 10,000 people are also feared to have been injured in Beichuan county.
Desperate efforts are under way to find survivors. One school that collapsed has buried an estimated 900 students.
BBC NEWS | World | Asia-Pacific | 'Thousands dead' in Chinese quake