The number of dead from China's earthquake is now put at more than 13,000.

Chinese officials say the death toll is expected to rise further after reports of thousands of people being buried under rubble in one city alone.

A massive search and rescue operation is under way in the country's southwestern region after one of the most powerful earthquakes in decades.

It is thought that up to 100,000 people are missing after yesterday's 7.9 magnitude quake, which was felt as far away as Beijing and the Thai capital, Bangkok.

In the city of Dujiangyan, 900 students were buried when Juyuan Middle School collapsed. At least 50 are known to have died.

Speaking on RTÉ Radio’s News At One, RTÉ Foreign Editor Margaret Ward said she had seen 18 survivors brought out at the school.

There have been harrowing scenes as the bodies of those killed were taken to a tent to be identified by their families.

Read Margaret Ward's account of the rescue effort at Juyuan Middle School here

A team of 1,300 troops and army medics reached Wenchuan county this morning and immediately began searching for survivors and treating the injured.

However the military was forced to scrap plans to air-drop food and medical supplies to the worst-hit areas because of heavy rain.

Strong aftershocks, including one 6.1 magnitude tremor, have continued to hit Sichuan and its capital Chengdu.

Tens of thousands of people are feared dead and aid agencies are warning that the most urgent risk facing survivors is exposure.

Death toll expected to rise

The quake struck in the middle of the afternoon when schools, factories and offices were full, contributing to the high death toll.

Even at this stage, China's state-run Xinhua news agency has only managed to provide snapshots of the extent of the disaster, with the confirmed death toll expected to rise significantly.

Xinhua says at least 5,000 have died in the district of Beichuan, where 80% of buildings collapsed, including a school which buried hundreds of pupils and teachers.

'Several thousand' are reported dead or buried in a flattened factory nearby, while over 600 died and 2,300 were buried in Shifang city where there are reports of a major chemical leak.

More than 18,000 people are believed to be buried under debris in the city of Mianyang, where 3,629 people have been confirmed dead.

And at least 2,000 people have been killed and 4,800 buried in Mianzhu - an area near the epicentre which remains cut off from rescue workers.

The earthquake is the most powerful to have hit the country in 30 years.

The Department of Foreign Affairs has said that there are no reports of any Irish casualties caught up in the earthquake.

So far anyone travelling in the region from Ireland has been accounted for.

People who have concerns about relatives in the region can contact 01-4780822.