Beijing  - Several Chinese towns close to the epicentre of a devastating earthquake were nearly razed, a military relief officer said Wednesday, as the confirmed death toll rose to about 15,000 with tens of thousands of other people missing and feared dead.

Military helicopters flew aid, medical personnel and relief troops to isolated settlements near the epicentre of Monday's 7.8-magnitude quake in Wenchuan county in the south-western province of Sichuan.

But the extent of the damage and casualties in Wenchuan, which has a population of 105,000, remained unclear.

Transport and communications problems meant there was still "no way to estimate the number of missing and injured people" in the county's worst-hit townships, said Wang Yi, the head of an elite People's Armed Police unit.

"In eight townships - including Yingxiu, Xuankou and Wolong - the losses are relatively serious," Wang told the state broadcaster CCTV from Wenchuan.

"Some towns basically have no buildings left," he said. "They have all been razed to the ground, and the losses are now being assessed."

More than one-third of the buildings had also collapsed in Wenchuan county town, reports said.

Army helicopters dropped several loads of food, drinking water and medicine in Yingxiu Wednesday.

They later airlifted at least 47 of the most seriously injured people from Wenchuan to hospitals in the provincial capital, Chengdu.

About 100 paratroopers also landed later in several areas of Wenchuan, where state media said up to 60,000 people were still out of contact with authorities.

Premier Wen Jiabao flew by helicopter to oversee relief work in Yingxiu and then returned to Chengdu.

Heavy rain had initially prevented helicopters from flying emergency aid to Wenchuan while troops were still trying to restore two badly damaged main roads to the county town.

Several military speed boats were also used to ferry people and supplies along the Min river from Dujiangyan to Yingxiu.

Workers and engineers rushed to build a temporary outlet from the Tulong reservoir on the river after quake damage caused a build-up of water and cracks in the dam at the Zipingpu hydropower station, threatening to flood Dujiangyan.

Paratroopers who gave an initial report to state media Wednesday from isolated Maoxian county said they two more dams were at risk of breaking at hydropower stations that were "severely damaged" during the quake.

Some troops walked Tuesday to Yingxiu, one of the worst affected towns in Wenchuan, and the military later said at least 500 people were confirmed dead in the area.

He Biao, the deputy head of Aba prefecture, which administers Wenchuan, said about 2,300 people out of Yingxiu's population of more than 10,000 were known to have survived the quake, and more than 1,000 of the survivors were badly injured, He said.

The survivors desperately needed medical help, food and water, he said.

The first 1,300 soldiers had arrived in areas of Wenchuan by midafternoon Tuesday, and many more were expected to arrive Wednesday out of the 100,000 troops and armed police sent to Sichuan.

The nearby city of Mianyang reported more than 7,000 dead and an estimated 18,000 buried in collapsed buildings.

Another 10,000 were missing in nearby Mianzhu, where 3,000 were already confirmed dead.

Civilian and military rescue teams pulled dozens more people alive from rubble in Yingxiu and several other areas of Sichuan on Wednesday.

The official death toll had risen to 14,866 by Wednesday afternoon, including about 400 in provinces bordering Sichuan.

The central government allocated 860 million yuan (123 million dollars) for relief operations while the Chinese Red Cross collected 65 million yuan, and donations were promised by many foreign governments.

The earthquake was felt in cities hundreds of kilometres away, including Beijing, Shanghai, Hong Kong and Bangkok.

It was the deadliest earthquake in China since 1976 when an estimated 242,000 people died in the northern city of Tangshan near Beijing. (dpa)