The death toll from the earthquake that rocked China on Monday could reach more than 50,000.

The latest figures have been reported by the official Xinhua news agency, which quoted rescue headquarters.

Some 20,000 have already been confirmed dead as a result of the 7.9-magnitude quake, and tens of thousands more remain buried in rubble in areas of the worst-hit province of Sichuan.

About 130,000 troops are assisting the search and rescue effort.

More than 12.5 tonnes of relief goods have been air-dropped and scores of helicopters are flying in rescuers and aid.

The Foreign Ministry said quilts, tents, food, satellite phones, medicine and excavators were needed most.

But in some villages near the badly hit area of Beichuan, angry residents complained they had had little to eat and were forced to drink contaminated water.

Many are sleeping outside or in makeshift shelters where the lack of water and blocked toilets has raised fears of outbreaks of diarrhoea and other infectious disease.

Meanwhile, a group of 19 British nationals who were on a panda-watching holiday when the earthquake struck have been found safe and well.

The Foreign Office said 14 members of the group were flown from the Wolong panda reserve in Wenchuan county to Chengdu by helicopter.

Diane Atkins, 63, from Portchester, Hampshire, who was evacuated with her 64-year-old husband David, said: "We looked around and everybody was running and rocks were falling and then we looked up and the mountain just seemed to explode."

"We thought we were going to be buried alive. I really thought we were going to die."

Fellow traveller Barry Jackson said: "Suddenly we had this horrendous noise which was just - you can't describe what it's like, it's just a huge, huge noise and the land shaking underneath you and the first thing that we all thought to do was to run."

Prime Minister Gordon Brown said: "I know there has been an enormous number of casualties and I want to send my condolences both to the government of China and the Chinese people.

"I know that in the last day or two, 19 British citizens who people feared were lost have been found. I know there may still be other Britons where contact has not yet been made. I hope that they will also be found safe."

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