Chinese police detained at least ten people for spreading rumours about the H7N9 bird flu virus, state media said, as the death toll from the new strain rose to nine.

Authorities detained the people in six provinces, some of whom had posted "fake information" online about new cases of the virus in their areas, the official Xinhua news agency said.

The death toll and number of infections in China from the strain of bird flu first found in humans last month has increased daily.

Nine people have died out of 33 confirmed cases of the virus, all in eastern China, according to data from the National Health and Family Planning Commission.

State media quoted authorities as saying a vaccine should be ready within months.

Until today, the source of the virus was not known, but Chinese researchers said they had traced it to wild birds and chickens, Xinhua reported.

One man detained in Anhui province was given seven days of administrative detention for fabricating posts on microblogs about infections, Xinhua said.

The Xi'an city public security bureau in Shaanxi province is investigating another man's posts, "to prevent untrue information from causing public panic," Xinhua said.

Scientists around the world have praised China for its handling of the deadly outbreak, but many Chinese people are sceptical of the government's pronouncements about the H7N9 virus, given a history of public health scandals and cover-ups.

The government initially tried to conceal an outbreak of Severe Acute Respiratory Syndrome (SARS), which emerged in China in 2002 and killed about one in ten of the 8,000 people it infected worldwide.

Chinese internet users have questioned why the government waited weeks to announce cases of the bird flu strain, but health officials said it took time to identify the virus, which was previously unknown in humans.

China's Communist Party is very keen to maintain social stability, but it has struggled to clamp down on rumours, which often spread quickly on the internet.

Authorities have detained people in the past for rumours, including 93 people accused of circulating information about the apocalypse last December.

Still, some commentators have noted that reports of a flu-like condition killing one person near Shanghai had been circulating on Chinese microblogs weeks before the government confirmed it was a case of H7N9.

"From this you can see if the government tried to cover up like in 2003, but more and more of these posts surfaced, there would be no way to conceal it," social media watcher and journalist Wu Heng said.

The latest H7N9 victim was from Anhui province, Xinhua reported.