Some 20 000 are confirmed dead after Monday's 7.9 magnitude quake and 25 000 were buried in areas rescuers have struggled to reach, battling landslides, buckled roads and collapsed bridges.

The Communist Party told officials to "ensure social stability" as the quake spawned rumours of chemical spills, fears of dam bursts and scenes of collective desperation.

Xinhua news agency said 17 "malicious rumormongers" had been punished for spreading "false information, sensational statements and sapping public confidence."

Rescuers in the city of Dujiangyan, in the worst-hit province of Sichuan, wrapped corpses dragged from the rubble in tarpaulins and sped them to morgues.

They were so busy that a notice outside one collapsed school asked parents to search for missing children in shifts.

About 130 000 army and paramilitary troops assisted the search and rescue effort in Sichuan, sifting through dozens of towns turned to rubble.

But three days after the quake, hopes of pulling survivors from the ruins dimmed and the waves of rescuers appear to be hampered by lack of specialised equipment.

Still, there were moments of joy and relief.

"Thank you, thank you," one 22-year-old said after she was eventually pulled to safety, covering her face against the light in Dujiangyan.

She had been trapped, unable to move, under the ruins of a hospital.

A teenage girl told Xinua how she and her classmates sang pop songs together as they lay trapped and injured in the ruins of their high school.

Li Anning, 16, was trapped for 40 hours in the rubble of the five-storey school before People's Liberation Army soldiers rescued her.

The strains from tens of thousands of homeless were also growing.

"There is enough food but not enough water.

We have only had bottled mineral water the past few days, nothing to cook with," said Wang Yujie, a teacher whose school withstood the quake.

More aid was arriving and efforts at coordination were also improving, with Sichuan setting up a hotline for victims and ambulances with Beijing licence plates on the roads.

More than 12,5 tonnes of relief goods had been airdropped and scores of helicopters were flying in rescuers and aid.

Officials said quilts, tents, food and satellite phones were needed most.

The Health Ministry's Gao Qiang said medical needs ranged from basics like bandages and antibiotics to sophisticated equipment such as ventilators and kidney dialysis machines.

Nampa-Reuters

World News Headlines Of The Last 48 Hours