Soldiers in the city of Mianzu search for thousands believed to be buried in the rubble [AFP]

Powerful aftershocks have shaken China's southwestern province of Sichuan a day after a deadly earthquake killed at least 12,000 people, many of them children buried in the rubble of collapsed schools.

 

Thousands more are reported to be missing after the magnitude 7.9 quake hit a day earlier and officials have warned the death toll is likely to rise much further.

 

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State media reported on Tuesday afternoon that rescue workers had reached the epicentre in Wenchuan county.

 

Rescue workers say that 3,629 people have died in Mainying city, which lies close to the epicentre of the earthquake, according to Xinhua state news agency.

 

Up to 18,645 people are buried under debris in the city, Xinhua reported.

 

Al Jazeera correspondent Melissa Chan, who is in the quake zone, said soldiers had been parachuted into the area or had trekked in on foot after roads were blocked with fallen trees and boulders.

 

She said bad weather was making rescue work difficult and exacerbating landslides triggered by the quake.

 

With shocks continuing to hit the region, many survivors in the worst-hit areas have taken to living on the streets, afraid to return to possibly weakened buildings.

 

Rescue workers meanwhile are continuing to race against time, digging through tonnes of debris in the hope of finding survivors trapped in the rubble.

 

In the city of Mianzu, near to the quake epicentre, almost 5,000 people were believed to have been buried under the remains of collapsed buildings, Xinhua reported.

 

The magnitude 7.9 quake which struck on Monday was the most powerful to hit China in three decades.

 

The first tremor hit at 2:48pm local time (06:28 GMT) with its epicentre 92km northwest of Chengdu, the capital of Sichuan province.

 

Schools hit

 

People across China have been asked to donate
blood to treat survivors [AFP]
Many of the victims were schoolchildren who were in class at the time the quake hit.

 

In the city of Dujiangyan close to the epicentre, rescuers were digging through the remains of a school, trying to locate 900 children who were in the building when it collapsed.

 

Chan said the bodies of at least 200 children had been pulled from the rubble of one collapsed school outside of Chengdu.

 

In the industrial city of Shifeng hundreds of people were buried and more than 6,000 evacuated after two chemical plants collapsed.

 

The collapse triggered a spill of about 80 tonnes of toxic ammonia.

 

Casualties have also been reported in the municipality of Chongqing, home to about 30 million people, which borders Sichuan province.

 

The massive Three Gorges Dam, located several hundred kilometres to the west of the quake zone, was not damaged, officials have said.

 

The United States, the European Union, Russia and Japan have all offered sympathy and pledges of help.

 

Taiwan has also offered to send emergency aid and rescue workers.

 

Soldiers deployed

 

The quake is the most powerful to
hit China in three decades [AFP]
About 20,000 police and soldiers have been deployed to the disaster area, with Wen Jiabao, the Chinese premier, in the region to oversee recovery efforts.

 

"The situation is worse than we previously estimated and we need more people here to help," he said at the emergency co-ordination centre.

 

"So long as there's a glimmer of hope, we will make every effort. We will not rest."

 

Hu Jintao, the Chinese president, has called for an "all out" effort to rescue victims.

 

Monday's initial quake lasted for several minutes and was powerful enough to be felt across several cities in South-East Asia, including Bangkok, the Thai capital, more than 1,800km from the epicentre.

 

China's deadliest quake in recent memory hit the eastern city of Tangshan in 1976.

 

The magnitude 7.8 earthquake was followed by an equally powerful aftershock almost a day later; together they killed around 240,000 people.

Source: Al Jazeera and agencies