People in southern China have cleared pharmacy shelves of medicines in panic after a mystery lung-based virus killed six people and laid low more than 300.

The scare has also spread to Hong Kong, where the price of vinegar - believed to prevent viral infections - has rocketed ten-fold, according to local reports.

There is no need for the people to panic Guangzhou city spokesman

Officials in Guangdong province, where the pneumonia-type virus first appeared two months ago, appealed for calm on Tuesday, saying the outbreak was under control.

But with rumours fuelled by popular internet chat rooms - one said 30 people had died in a single office building - people throughout the province have snapped up traditional Chinese and Western medicines along with surgical masks.

The scare even boosted shares in China's fledgling stock market as investors rushed to buy shares in pharmaceutical companies.

Health advice

Guangdong health officials said on Tuesday that 305 people had been infected with the virus, officially termed an "atypical pneumonia", with six dying.

Ruling out wilder rumours that anthrax or plague were to blame, health bureau chief Huang Jionglie said the epidemic had begun in hospitals, according to the official Xinhua news agency.

"Everyone should follow the government's instructions, maintain a distance from those afflicted by the disease, keep good air circulation in the workplace and avoid fatigue," said a spokesman for the bustling commercial city of Guangzhou.

"There is no need for the people to panic."

Hong Kong was hit by bird flu panics

In neighbouring Hong Kong, which has been hit by a series of public health scares in recent years over the so-called bird flu, officials tried to dampen fears. They said there was no evidence the virus had yet hit the former British colony.

But locals were taking no chances.

"We ran out of herbal medicines in the morning," the owner of a traditional Chinese medicine dispensary in Hong Kong told reporters.

And according to the territory's Mingpao Daily, vinegar prices have shot up, with the price of a large bottle reaching more than $10.

An outbreak of bird flu in Hong Kong in 1997, beginning in the poultry industry, killed six people and prompted the territory to slaughter all of its 1.4 million chickens.