As troops reached the quake-battered areas near the epicentre, the state media reported that the death toll in Mianyang city alone rose from 3629 to 5,540 with 18,486 more buried and 1,396 missing.

In Yingxiu of Wenchuan county, only 2,300 people were believed to have survived out of 10,000 people living in the town near the epicentre, official Xinhua news agency said.

It had earlier reported a toll of over 12,000 in the quake. The toll was expected to rise further once rescuers reach other towns in Wenchuan.

Some towns near the epicentre have been "razed to the ground" with no houses left standing, a police official was quoted by the state media as saying.

"The losses have been severe. Some towns basically have no houses left. They have all been razed to the ground," Wang Yi, head of an armed police unit sent into the disaster zone, was quoted as saying by Sichuan Online news site.

Around 20,000 soldiers had landed in the disaster-struck areas, another 30,000 en route by air, road and rail and on foot and the People's Liberation Army (PLA) has ordered 30,000 more troops to reinforce the disaster relief, the agency said.