CHENGDU, China (AFP) - - A man who survived China's earthquake by drinking sweetened water through a straw was pulled from the rubble Tuesday after eight days, but hopes faded for others as the death toll topped 40,000.

With flags at half-mast on the second day of official mourning, tens of thousands of jittery residents in the major city of Chengdu ran for cover after authorities warned that more strong aftershocks could shake southwestern China.

Beijing also put out another urgent appeal for tents as foreign medical teams began to arrive on the scene to help care for the nearly 250,000 people injured in last Monday's earthquake, which measured 8.0 on the Richter scale.

Despite the overwhelming odds against finding any more survivors under the rubble, rescue workers Tuesday saved a man, Ma Yuanjiang, who had been buried for an amazing 179 hours, the state-run Xinhua news agency said.

Workers spent more than 30 hours trying to dig the 31-year-old power plant executive out of the rubble of a destroyed building, during which they fed him sugary water through a straw, Xinhua said.

Ma was surprisingly able to speak, eat and drink small amounts as he was rushed to hospital treatment, but his left forearm had to be amputated, it said.

Another man, Peng Guohua, was saved Monday in a lime mine after he drank his own urine to survive, according to state press.

Such improbable survival stories have inspired many Chinese, who on Monday came to an unprecedented three-minute standstill to honour the victims of the earthquake.

But the number of rescues has tapered off, and the frantic pace of searching for survivors in the endless rubble has slowed, as the reality sets in that finding any more people alive after so long is almost impossible.

The government said on Tuesday that the death toll from the earthquake had risen to 40,075. A cabinet spokesman said hours earlier the number of dead and missing was nearly 66,000.

Across southwestern China, tens of thousands of residents ran for safety early Tuesday on fears of another earthquake, carrying bedding, chairs, clothes and other possessions.

Giant traffic jams formed in Chengdu , the capital of Sichuan province with a population of over 11 million people, as drivers headed toward the suburbs or the city's open spaces such as parks, construction sites and stadiums.

"Anyone who says he is not afraid is just kidding," said Zhu Yuejin, a 23-year-old saleswoman who spent the night in a car.

A warning on the Sichuan government website, quoting seismological authorities, said that a strong aftershock of 6.0 to 7.0 magnitude would strike the same area ravaged by last week's massive tremor.

But Du Jianguo, a Beijing-based researcher with China's Institute of Earthquake Science, said it was impossible to predict aftershocks so accurately.

"I don't know who made such a forecast, but personally I don't believe it," he told AFP.

Fuelling fears among the superstitious, residents of the southern city of Zunyi reported a massive migration of frogs and toads, which also covered Sichuan towns days before the May 12 earthquake, according to state media.

China has been hit by more than 150 aftershocks measuring 4.0 or higher on the Richter scale since the initial tremor, including one overnight that measured 5.0.

That tremor appeared to cause further damage in the quake zone, which spans across 100,000 square kilometres (40,000 square miles) of mountainous Sichuan, an area roughly three times the size of Belgium.

In Beichuan county, one of the worst-hit areas, cranes that were being used for rescue work the previous day were tipped on their side, according to an AFP reporter there.

The warning of the powerful aftershock set off nerves on China's stock markets , contributing to a nearly 4.5 percent drop in share prices, dealers said.

China has seen a wave of sympathy over the earthquake, but international criticism started to build over China's decision to let in foreign rescuers only three days after the earthquake.

"There was a delay in the decision-making. It would have been better if the decision was quicker," Japanese Foreign Minister Masahiko Komura said in Tokyo.

The Japanese team, the first official foreign team on the scene, were heading home without finding any survivors, although another Japanese unit left Tuesday to provide medical relief.

Huang Qiong, a Chinese surgeon who has completed 100 operations since the earthquake, told the state-run China Daily that she had to stop herself crying as she worked.

"But when I go back home and lie down on my bed, I just cannot help shedding tears," she said.