As governments around the world worry about the possibility of a global epidemic of bird flu, one key player is China, where two new outbreaks have been reported within the last week. But while international organizations say China's management of the avian flu has become more transparent, scientists complain about restrictions in their research.

Doing research on avian flu in China is not an easy task. Few people know this better than Dr. Guan Yi, director of the Joint Influenza Research Center, a project between Hong Kong University and Shantou University in China's southern Guangdong province. He is one of the world's leading researchers on the H5N1 strain of avian influenza, which is potentially lethal to humans and has killed more than 60 people since it first appeared in 1997.

In July, Dr. Guan and his team published a groundbreaking article in an international scientific magazine. It said that infected migratory birds at a lake in western China appeared to have contracted the disease in southern China.

This meant that if the virus became established among migratory birds, it would raise the risk that it could spread across oceans and continents. Dr. Guan's thesis was validated by recent bird flu outbreaks in Europe.

But rather than supporting Dr. Guan's research, the Chinese Ministry of Agriculture criticized his findings through state-controlled news media, saying the paper had reached the wrong conclusions. Dr. Guan says authorities wanted to cover up the fact that the source of the infection was in southern China.

"They interpret this event that the source of the infection for birds in Qinghai Lake is from outside China, it looks like China is the victim not the source," said Dr. Guan.

Since then, the Chinese Ministry of Agriculture has introduced tightened control over research on infectious diseases. According to Dr. Guan, only three laboratories in China now are allowed to study H5N1. After the publication of Dr. Guan's article, his team's research on bird flu at Shantou University was severely restricted.

"The Ministry of Agriculture thinks to deal with the H5N1 is their business. They don't want other people to [be] involved to understand the true picture, then they can tell the story as they want, pick up selected information," he added. "They think if we tell the truth, the person sitting in a direct position, it is dangerous for his political future."

So far, almost all avian flu victims caught it from infected birds. But international health experts fear the H5N1 virus could change so that it spreads easily among humans, and once it does, it could sweep around the globe and kill millions.

Many experts think that China could be the epicenter of a bird-flu epidemic among humans. It is not only the most populous nation, but also the world's biggest poultry producer. Moreover, 70 million migrating wild waterfowl travel through China. It also is home to half the world's pigs, which can harbor human viruses that can combine with bird-flu bugs to form human pathogens.

Critics such as Dr. Guan are worried that the Chinese government has not learned from the SARS epidemic two years ago, when international health officials criticized Beijing for its slow response to the disease and secrecy about the outbreak.

SARS appeared in southern China but officials there said nothing about it for months, until it spread to Hong Kong and then traveled around the world, killing more than 800 people.

Several international organizations have complained about a lack of cooperation from China in dealing with the bird flu.

The Beijing office of the World Health Organization said this summer that authorities were slow in revealing vital information and in sharing virus samples of outbreaks in western China. They also initially did not respond when the organization asked to visit the site of a bird flu outbreak in China's northwest.

But Aphaluck Bhatiasevi, a W.H.O. spokeswoman in Beijing, says the cooperation from Chinese authorities has improved - following visits by two senior W.H.O. officials in August and September, who urged China to become more open.

"Recently we have seen a lot of development and commitment, and China is also in the process of providing information on the virus sequence to WHO," she said.

Joseph Domenech, the chief veterinary officer of the United Nation's Food and Agriculture Organization in Rome, also says that collaboration and communication with Chinese authorities has improved. But what worries him is the country's ability to spot outbreaks of avian flu and other diseases.

"We are not so much worried about the transparency of the information," he said. "We are more worried about the capacity of the Chinese system to get information from everywhere in such a huge country; it is rather decentralized."

International experts say China does not have enough people to quickly identify bird flu and report it to central authorities. That means outbreaks could spread rapidly before they are detected.

While China's surveillance system is a concern, international organizations such as the FAO say that authorities have responded swiftly whenever an outbreak of avian flu has been reported.

Last week, for example, China destroyed more than 90,000 birds and implemented quarantine measures to stop a bird flu outbreak in Inner Mongolia. And on Tuesday, the U.N. Food and Agriculture Organization said 45,000 birds had been culled in eastern Anhui province, after more than 2,000 geese and chickens became infected with the disease.