Chinese state media say more than 18,000 people were buried in one city in southwestern China's Sichuan province during Monday's massive earthquake, and that almost 3,100 of them are confirmed dead.
The new figures from Mianyang city pushes the death toll from the 7.9 magnitude earthquake, China's worst in decades, to more than 12,000 people.
Mianyang is nearby Wenchuan County, the epicenter of Monday's quake.
News of the rising death toll comes as the first rescue and relief troops arrived in Wenchuan county, home to more than 100,000 people. The number of casualties there is still unknown.
More than 50,000 troops have been sent to assist with relief work and to help dig out thousands who remain buried under collapsed buildings and schools.
Officials say at least 2,000 people are dead in the the city of Mianzhu, and 4,800 buried.
In the city of Dujiangyan, Xinhua says rescue workers pulled 60 bodies from a collapsed school where 900 students are believed to have been trapped.
Landslides have left boulders blocking the road to Beichuan county, preventing rescuers from reaching an area where authorities estimate that at least five thousand people died.
Local officials say they have recorded more than one thousand aftershocks, some as strong as magnitude six.
Officials say at least 80 percent of the buildings in Beichuan have collapsed. In addition to the dead, 10,000 more people are feared injured.
Two chemical plants in Sichuan also have been damaged, burying hundreds of people and forcing the evacuation of several thousand others.
Some information for this report was provided by AFP, AP and Reuters.