May has already been a particularly brutal month for natural disasters, with the Burma cyclone, tornadoes in the U.S. and, most recently, the devastating earthquake in China, which seismologists say registered at magnitude 7.9. Rescue efforts near the epicenter have been hindered by rain and aftershocks, but with thousands still trapped in the wreckage every minute counts.
Troops have arrived in Wenchuan county at the epicentre, which was largely cut off by the quake—but heavy rain is hampering rescue operations.
Elsewhere in Sichuan province, frantic efforts are being made to reach thousands of people under the rubble.
The death toll is now more than 12,000, officials say, and looks set to rise.
Chinese rescuers search a collapsed building for survivors in Beichuan, Sichuan province, on Tuesday.
In one city, Mianyang, near the epicentre, more than 18,000 people are said to be buried under the rubble, state news agency Xinhua reports.
In the nearby town of Mianzhu, at least 4,800 people are trapped, and massive landslides have buried roads to outlying villages, state news agency Xinhua says.