China has slapped poultry export bans on three more areas amid a World Health Organization warning that the chance of controlling the outbreak is slipping.
Thailand's handling of the disease has been described as a "screw up"
Exports of poultry and related products have been halted from Shanghai and the provinces of Anhui and Guangdong as suspected cases there are investigated.
Guangdong is on the alert for attempts to smuggle poultry to the lucrative nearby markets of Hong Kong and Macau.
The WHO has said China may be missing a "brief" chance to halt the outbreak.
"We have repeatedly said there is a brief window of
opportunity to act within China," said Dr Julie Hall, a WHO
official in Beijing.
News of the suspected outbreaks in the three new areas "strongly suggests that the window is getting smaller with each passing day", she added.
Outbreaks of the lethal H5N1 strain of bird flu were earlier confirmed in the provinces of Guangxi, Hubei and Hunan.
Health officials descended on farms in the Shanghai area without warning on Friday, seizing tens of thousands of birds, spraying disinfectant and burning chicken dung.
AVIAN FLU ALERT
First jumped "species barrier" from bird to human in 1997
There are no known instances of the virus being passed between humans
In humans, symptoms include fever, sore throat and cough
Types which threaten humans are influenza A subtypes H5N1 and H9N2
"If bird flu is really upon us, our business will take a
big hit," one worried worker, who did not give his full name, told Reuters news agency at Shanghai's wholesale Fowl and Egg Market.
The seizure of birds without promise of compensation in the absence of confirmed cases also provoked anger as a farmer in Shanghai's southern district of Nanhui told Reuters.
"All our chickens were fine," said Lao Gu. "There was nothing wrong with them. Look at me, do I look sick to you? We've lost tens of thousands of yuan. It's the [Communist] Party's fault."
The BBC's Francis Marcus reports from Shanghai that there are fears China could become a huge incubator for the virus if new cases are confirmed.
The current bird flu epidemic has affected 10 Asian states, killing at least eight people in Thailand and Vietnam.