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BEIJING, May 18 (Reuters) - Three people were killed and more than 1,000 injured when an aftershock hit Jiangyou city in earthquake-devastated southwestern China early on Sunday, state news agency Xinhua reported.

The 5.7 magnitude tremor shook Sichuan province six days after a massive tremor killed tens of thousands of people in the same area.

Xinhua reported that the aftershock had brought down a large number of houses, damaged 377 km (230 miles) of roads and six bridges.

The tremor also caused thousands to flee swaying buildings in the provincial capital, Chengdu, some 200 km (125 miles) south of the aftershock's epicentre.

USGS said the quake, which follows hundreds of slightly less strong aftershocks during the week, was nearly 50 miles (80 km) deep and hit 49 miles (80 km) west of Guangyuan.

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