A 6.4 magnitude aftershock on Sunday has killed six people and injured nearly one thousand in southwest and northwest China, according to local government sources.

Four people were confirmed dead and 20 others were seriously injured in Hanzhong City of the northwestern Shaanxi Province, said mayor Hu Runze on Monday.

Hu said all the four dead were in a paddy field of Xixiang County when the aftershock occurred.

He said investigation had started for detailed losses caused by the aftershock, the strongest tremor since the 8.0-magnitude May 12 quake.

In Qingchuan County of Sichuan, the epicenter of the aftershock, one was killed and more than 700 people had been injured while nine villages and towns suffered telecommunication cutoff, according to the disaster relief headquarters in the county.

Longnan City in northwest Gansu Province reported one death and 109 injuries with 15 in serious condition. The victim was killed by the rolling stones from a mountain.

The aftershock, which was felt in many parts of the country, also destroyed or severely damaged about 270,000 houses.