Tremors were felt 200 km (120 miles) away to the north and south.

"The dead included a 4-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," Xinhua said. "The mother was rescued but the boy was killed."

Xinhua earlier told a Hong Kong television station a 4-year-old girl was among the dead. It was not clear if the two child victims were one and the same.

Power was cut to the city and the only communications possible were by mobile phone, a local official said. The quake forced the evacuation of 120,000 residents, Xinhua quoted a provincial civil affairs department official as saying.

Some mostly mud-and-brick houses had collapsed and roads were destroyed, state TV said. Water and power supplies were damaged.

The quake hit at 5:34 a.m. (2134 GMT Saturday) and one Pu'er office worker named Li said it had woken her in her fifth-floor apartment.

"I tried to get up but the tremor was too strong. It cracked the window panes," she told Reuters.

She was called to her office, where she saw soldiers and armed police rushing down the street as rescue operations began.

President Hu Jintao, Premier Wen Jiabao and Vice-Premier Hui Liangyu had asked provincial government officials "to mobilise all resources available to treat the injured and minimise the loss of lives and property", Xinhua said.

Coal mines in the area were ordered to suspend operations and evacuate all workers.

The Pu'er city government had allocated 1 million yuan (US$131,000) for relief, Xinhua said. The provincial civil affairs department was sending 2,000 tents, 2,000 quilts and 2,000 items of clothing to the stricken area.

Ning'er county, covering an area of 3,670 sq km (1,400 sq miles) within the city limits, has a population of 190,000.

Pu'er, home of the tea of the same name, lies near to the border with Myanmar, Laos and Vietnam. The epicentre of the quake was 23.0 degrees north and 101.1 degrees east.