A man in the Chinese province of Zhejiang has died of the H7N9 strain of bird flu, state media said Wednesday, bringing the total deaths attributed to the virus to three since the first human cases.

He was one of two H7N9 avian influenza infections reported in Zhejiang in eastern China, the official Xinhua news agency said, citing local authorities, bringing the country's total number of cases to nine.

Chinese authorities are trying to determine how exactly the new variety of bird flu infected people, but say there is no evidence yet of human-to-human transmission.

The latest fatality was a 38-year-old man who worked as a chef, media website Zhejiang Online said. The province's other case was a 67-year-old retiree who was being treated in hospital.

Two other deaths have been reported, both in China's commercial hub of Shanghai. Other cases have occurred in the eastern provinces of Jiangsu and Anhui, the government has said.

The World Health Organisation on Wednesday said the number of cases of the infection looks set to climb, but a pandemic is not on the cards.

"Given the fact that we've seen seven confirmed cases, plus there are reports of other cases, it would not be surprising to see additional cases," said Gregory Hartl, spokesman of the WHO's influenza and epidemics division.

"But these would be additional cases, one by one. We have no evidence so far of human-to-human transmission, and without human-to-human transmission, the likelihood or risk of pandemic is low," he told reporters.

"We're a long way away from thinking about a pandemic," he added.

Malik Peiris, Chair Professor of the Virology School of Public Health at the University of Hong Kong, said identifying the source of the virus was urgent.

"If one can identify that, then you have possible interventions to reduce human exposure and ideally to stamp out the virus in that particular poultry reservoir," he told AFP.

China's neighbour Vietnam has announced an immediate ban on all Chinese poultry imports and stepped up border controls in response to the outbreak.

Hanoi has imposed the ban to "actively and efficiently prevent the intrusion of the H7N9 virus into Vietnam", according to an urgent message signed by the Minister of Agriculture Cao Duc Phat.

Taiwan, which is separated from mainland China by a narrow strait, said Wednesday it had raised its level of alert and set up a group tasked with preparing to prevent a possible epidemic.

In Shanghai, where two people have died from the virus, some residents expressed worries over eating poultry.

"I'll stop buying chickens for the moment and wait until the situation eases," said a middle-aged woman at a traditional food market.

Shanghai officials have assured people that the city's chicken and pork are safe to eat, after the H7N9 cases and the recovery of more than 16,000 dead pigs from the city's main river last month, but many are unconvinced.

China is considered one of the countries at greater risk from bird flu because it is one of the world's biggest poultry producers and many chickens in rural areas are kept close to humans.

The more common strain of avian flu, H5N1, has killed more than 360 people globally from 2003 until March 12 this year, according to the World Health Organization.