Two men in masks and protective suits guarded the border between Beijing (search) and Hebei province, watching for vehicles transporting live poultry under anti-bird flu measures announced Monday to protect the capital.

Only shipments of live chickens, ducks and geese from three certified Hebei farms are allowed in, said Tian Zhigang, an animal quarantine officer at the Baimiao Inspection Station.

The rest will be turned back after the vehicle is sprayed with disinfectant from a huge plastic tank.

"We use our eyes and ears," Tian told reporters on a trip organized by the Beijing city government. "It's 24-hour surveillance."

China (search) has reported four outbreaks of bird flu since Oct. 14 but has no confirmed human cases. Still, it has been imposing increasingly rigorous measures to prevent outbreaks among its 5.2 billion chickens, ducks and other poultry following warnings that a human case is inevitable if China cannot stop its fowl from getting sick.

In addition to showing off its efforts to journalists, the government has launched campaigns to educate the public -- a stark contrast to its initially secretive handling of an outbreak of severe acute respiratory syndrome, or SARS (search), in 2002.

Health Minister Gao Qiang urged more stringent surveillance, prevention and control measures to make sure bird flu doesn't spread to humans. "It's long-term, it's complex, it's important," Gao said Monday in a statement posted on the ministry's Web site.

The H5N1 (search) virus has killed least 62 people across Southeast Asia since 2003. Those victims had contact with infected birds, but health experts warn the virus could mutate into a strain easily spread from person to person, setting off a pandemic that could kill millions.

Experts are especially worried about China because of the vast scale of its poultry industry and because it is a major migration route for wild birds.

The official Xinhua News Agency (search) said Monday that 6 million poultry in 15 villages were destroyed in the northeastern province of Liaoning, site of the most recent bird flu outbreak that killed 8,940 chickens.

The slaughter was carried out because of rules requiring the destruction of all birds within two miles of an infection site, Xinhua said.

In Beijing, more than 20 million birds have been vaccinated, though the city has no suspected bird flu cases, said Liu Yaping, deputy director-general of the capital's Agriculture Bureau.

All 168 live poultry markets were shut down Monday, and authorities are going door-to-door seizing chickens and ducks being raised in private homes.

Health workers also are patrolling zoos, lakes and parks looking for sick or dead birds, and some 2,500 "high risk" people -- those who work closely with poultry -- have been tested but all are healthy, Liu said.

Reporters were also taken to a market in Baliqiao (search), 18 miles east of central Beijing. A section that once sold 2,000 live chickens, ducks and geese a day was closed, but another the market was selling chicken parts -- thighs, breasts, hearts, heads, gizzards, livers, necks -- piled high on metal trays.

Vendors said the meat was from Beijing slaughterhouses and had been certified by inspectors. Eating properly handled and cooked poultry is safe.

"More and more people are eating chicken because Beijing has no bird flu and because they believe that the meat is safe," said Deng Zhuyi, who insists sales have doubled in recent days.

But Ma, a vendor who gave only her surname, said bird flu is "messing things up."

"People are becoming afraid to eat it lately," she said. "Restaurants and families are buying half as much as they did just a little while ago."

Customers poked and prodded the chicken pieces with their bare hands.

Zhao Anji, 30, bought some drumsticks for dinner.

"My guests asked for chicken," he said. "But for myself, I don't feel too comfortable eating it. I will tonight, but maybe not again for a while."