THOUSANDS of Chinese fled for cover in fear of an earthquake today, alarmed not only by warnings from seismologists but also by an unusual mass movement of frogs, state media said.

For the second time this month, residents observed a huge migration of frogs and toads, the state-run Xinhua news agency said.

Residents of Zunyi, a southern city that saw little damage in China's huge earthquake last week, noticed the amphibians' march yesterday, Xinhua said, quoting Vice Mayor Zeng Yongtao.

Thousands of residents camped out in fear overnight in downtown Zunyi, the news agency said.

"We don't know what else we can do,'' Zunyi resident Liu Yong was quoted as saying.

Their decision to move outdoors coincided with a warning from seismological authorities that there may be another big aftershock in southwestern China's Sichuan province today following last week's tremor.

The May 12 earthquake - which left more than 71,000 people dead, missing or buried in rubble - also came after reports of unusual movement of frogs and toads.

Internet blogs showed footage of frogs and toads covering the streets of Mianyang in the days before the town in Sichuan province was ravaged by the earthquake.

Many people, at least in retrospect, took them as an omen of disaster.

Others said that the frogs and toads had come to welcome the Beijing Olympic flame.

Local forestry officials had said the movement was simply because it was mating season, although their explanations were attacked on China's lively internet discussion boards.

Superstitious Chinese have looked for cosmic explanations for the earthquake, the country's deadliest natural disaster in three decades.

Many noted that the earthquake occurred exactly 88 days before the Beijing Olympics, which opens on August 8 - 8/8/8 - at 8:08 pm, in line with Chinese numerology which considers eight a lucky number.

Speculation was heightened on Sunday when China's seismological authority revised up the magnitude of the May 12 earthquake to 8.0 on the Richter scale.