The tremor, the strongest aftershock since the May 12 earthquake, hit Jiangyou city in Sichuan, Xinhua state news agency said, on the eve of three days of national mourning for the dead that now stands officially at 32,500.
The fresh tremor, which measured 5.7 in magnitude, brought down a large number of houses, damaged 377 km (235 miles) of roads and six bridges, rescue authorities said late on Sunday.
In the provincial capital, Chengdu, some 200 km (125 miles) south of the epicentre, thousands fled swaying buildings, Xinhua said.
More than six days after the main quake of 7.9 magnitude rattled Sichuan province, authorities are worried by the aftershocks and the build up of water in blocked rivers and have tried to stop people from entering the affected area.
Xinhua said the most dangerous mass of water was only about 3 km (2 miles) upstream from Beichuan town where rescue workers saved a man on Sunday from under the remains of a hospital.
China says it expects the final death toll to exceed 50,000. About 4.8 million people have lost their homes.
Three days of national mourning were declared from Monday, with flags flying at half mast, public entertainment suspended and a three-minute silence observed to mark exactly one week since the quake, the government website www.gov.cn said
State television said the Olympic torch relay through China would also be suspended for three days.
SURVIVOR'S LEG AMPUTATED
Late on Sunday, a woman was also pulled out of the rubble in Yingxiu after a 56-hour rescue operation during which her legs were amputated, Xinhua reported. A man was earlier found alive in a collapsed office building in Maoxian county, it said.
The overall death toll stands at nearly 32,500, Xinhua said, with 220,000 more injured. A further 9,500 people are thought to be still buried under the rubble in Sichuan, but most are feared dead.
