NING'ER, Yunnan Province, June 3 (Xinhua) -- Three people have been confirmed dead, and at least 300 injured after a strong earthquake measuring 6.4 on the Richter scale struck southwest China's Yunnan Province on Sunday.

The dead included a four-year-old boy, who was sleeping with his mother when the earth-built walls of their house collapsed in the quake and buried him and half of the body of his mother. The mother was rescued but the boy was killed.

The quake shook the old downtown area of Ning'er at 5:34 a.m., with the epicenter at 23 degrees north and 101.1 degrees east, according to the China Earthquake Administration.

Twenty seriously injured people had been transferred to the city's hospitals.

"The house was shaking hard," said Zhu Shoukang, a 60-year-old man in a residential area of the county. He was sleeping when the quake occurred. He immediately hid himself under the bed and managed to come out of the house during the intervals of the quake.

Zhu said he dared not return to his house, as it had crevices on its walls after the quake.

The quake, which affected 186,000 people in 35,000 households, also forced the evacuation of 120,000 residents, said a spokesman of the provincial civil affairs department. Many residents had moved to public areas as their houses either collapsed or were damaged.

The city's seismic bureau had recorded more than 300 aftershocks by 3:30 p.m. The strongest occurred at 10:49 a.m. with a magnitude of 5.1, centered at 23.02 degrees north and 101.06 degrees east.

Ning'er County, covering 3,670 square kilometers, has a population of 190,000. It had reported nine quakes measuring five or above on the Richter scale in history, with the strongest of 6.8 which happened on March 15, 1979.

More than 70 mobile phone signals transmission stations were severely damaged, making it difficult to make cell phone calls.

The county's power grid was also severely damaged with reduced capacity, while two mid-sized reservoirs were cracked.

Coal mines in Ning'er and surrounding areas were ordered to suspend operations with all workers evacuated from pits, said Duan Liyuan, head of the provincial work safety bureau.

The government of Pu'er City has allocated one million yuan for emergency relief. The provincial civil affairs department is sending 2,000 tents, 2,000 quilts and 2,000 items of clothes to the stricken area.

The Ministry of Civil Affairs has sent a working group to the area and allotted 5,000 tents from neighboring Guangxi Zhuang Autonomous Region.

The China Red Cross Society and its Yunnan branch have sent the first batch of relief supplies worth 500,000 yuan (65,000 U.S. dollars), including tents, quilts, food and medicines.

Pu'er City, called "Simao" before it was renamed on April 8, is prone to strong earthquakes. It has experienced 20 above a magnitude of five since 1990.

Pu'er, in southwest Yunnan, borders Vietnam, Laos and Myanmar and covers 45,000 square kilometers and has a population of 2.6 million.

Residents in Lincang City, about 200 kilometers from the epicenter, and Dai Autonomous Prefecture of Xishuangbanna, 300 kilometers from the center, also felt the tremor, but damage and casualty reports are not available.

Rescue officials from the China Earthquake Administration have been dispatched to help local rescue efforts.

The Yunnan government will budget three billion yuan for anti-earthquake project that will benefit one million poor families living in dangerous and shabby houses within 10 years. Every household can get 3,000 to 5,000 yuan of subsidies in restoring their houses.

The government sets a goal of making all rural residents' houses solid enough to resist earthquakes of 6.0 magnitude.

This year, the government invested 500 million yuan in the project covering 166,000 households in 70 counties.

During the 2001-2006 period, Yunnan recorded 27 earthquakes of at least five magnitude, causing 56 deaths, 2,123 injuries and nearly 3.6 billion yuan of losses.