China has suspended poultry and bird markets in Beijing as part of efforts to stop any spread of bird flu, officials said on Monday.
China has been hit by four bird flu outbreaks in three weeks
They also announced a major cull in the province hit by the latest outbreak.
The moves came as investigations continued into whether three Chinese people have contracted bird flu, one of whom - a 12-year-old girl - has died.
If found to have the disease, they would be the first known human cases in China.
Bird flu has already killed at least 62 people elsewhere in Asia since the outbreak began in late 2003.
The international community is still grappling with how to deal with the disease, and the fear that it could lead to a human pandemic if the virus mutated.
A major conference has just opened in Geneva, to discuss a worldwide plan of action.
The gathering brings together the World Health Organization, the World Bank, the UN's Food and Agricultural Organization and the World Organisation for Animal Health as well as top policy-makers from WHO member states.
China's Xinhua news agency said all poultry within a three-kilometre (two miles) radius of the latest outbreak - in Liaoning's Heishan County - where the deadly H5N1 strain of the virus was found last week, have now been killed.
Sunday's culling operation involved 1,700 government workers and 100 police officers.
Free medical checks are being offered to residents while poultry in unaffected places in the vicinity are being vaccinated, state-run media said.
Chinese Agriculture Minister Du Qinglin had earlier said that it was "imperative to act early, quickly and strictly" against the virus.
Beijing has also asked WHO experts to investigate whether bird flu was responsible for the death last month of a 12-year-old girl in the central province of Hunan.
The girl died with symptoms similar to pneumonia following a nearby bird flu outbreak, while her brother and a teacher from a different county have recovered after falling ill.
China initially said the three were all ill with pneumonia.
"The three cases have been diagnosed as pneumonia of unknown cause, but we cannot rule out the possibility of human infection of the H5N1 avian influenza," the Chinese health ministry said.
Experts are especially worried about bird flu in China because of the vast scale of its poultry industry and the fact the country is a major migration route for wild birds which can spread the virus to other areas.
But other nations in Asia are also struggling with their own battles against bird flu.
Indonesia recently confirmed its latest bird flu case - eight-year-old Ilham Junaedi.
Ilham Junaedi is a close relative of 19-year-old Ina Solati, who died of the disease in Tanggerang on 28 October.
EU Health Commissioner Markos Kyprianou said the European Union would give 30 million euros [about $35.5m] to help Asia fight bird flu.
Speaking in Vietnam at the start of a 10-day tour of Asian countries hit by the disease, he admitted the EU "should have reacted more quickly to help South East Asia to tackle the problem".
"It's better late than never," he said. The EU is interested in co-operating with Asia to solve the problem."
BIRD FLU OUTBREAKS IN 2005 (H5N1 STRAIN)
The H5N1 strain remained largely in South-East Asia until this summer, when Russia and Kazakhstan both reported outbreaks
Scientists fear it may be carried by migrating birds to Europe and Africa but say it is hard to prove a direct link with bird migration
EU has banned the import of captive live birds