China confirmed three more cases of H7N9 bird flu, two in Shanghai and one in Anhui, while Nanjing become the second mainland city to ban live poultry sales.
The latest cases in Shanghai and Anhui brought the total number of confirmed H7N9 cases across the nation to 21 - ten in Shanghai, six in Jiangsu, three in Zhejiang and two in Anhui. Four patients in Shanghai and two in Zhejiang have died.
Hong Kong's government said it could not rule out the possibility of an outbreak in the city.
Local governments in the Yangtze river delta stepped up efforts to contain the virus as it was found in more live poultry.
Authorities in Nanjing, the Jiangsu capital, closed all wholesale markets at dawn yesterday. All remaining live poultry was culled in Shanghai after 20,000 birds were killed on Friday.
In Hangzhou, authorities closed a farmers' market after the virus was detected in live quails. One of the current patients had eaten quail sold there.
The National Health and Family Planning Commission said the cases so far were isolated and there was no evidence of human-to-human transmission.
The China Food and Drug Administration fast-tracked approval for the intravenous anti-influenza drug Peramivir.
Mao Qunan, director of the China Health Education Centre, said on the sidelines of the Boao Forum for Asia in Hainan that although there was no evidence of human-to-human transmission, the possibility should not be ruled out.
Leaders including President Xi Jinping and Premier Li Keqiang promised transparency in reporting of the virus.
The Hong Kong government said precautions were in place to cope with an outbreak.
Secretary for Food and Health Dr Ko Wing-man said yesterday: "We have to be prepared that H7N9, no matter if it's in poultry or humans, may appear in Hong Kong. The possibility can't be excluded."
Ko said the Hospital Authority could handle a reasonably large- scale outbreak and had 1,400 isolation beds available - in line with the government's strategy to identify and isolate suspected sufferers early.
Chief Executive Leung Chun-ying said the city had sufficient "disease prevention supplies" and there was "no need for panic buying".
About 30 pupils from Sheung Shui Wai Chow Public School left for Shanghai yesterday for a scheduled four-day study tour.
School principal Chan Siu-hung said the tour was planned three months ago and could not be cancelled. But in light of the bird flu outbreak, they would cancel visits to crowded places.
In Nanjing, residents posted pictures of dozens of dead sparrows found on Friday, which circulated widely online.
View H7N9 map  in a larger map
Click on each balloon for more information on individual patients infected with the avian flu virus: blue, patients infected with the H7N9 virus under treatment; red, those infected with H7N9 who have died; and pink, those infect with the H1N1 avian flu virus.