Chinese police detained at least 10 people for spreading rumours about the H7N9 bird flu, state media said on Wednesday, as the death toll from the new strain of the virus rose to nine.

Authorities detained the people in six provinces -- Shaanxi, Guizhou, Jiangsu, Zhejiang, Anhui and Fujian -- 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 ticked up daily.

Nine people have died from the 31 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.

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

The Xi'an 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 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 10 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 (SARS cases) but more and more of these posts surfaced, there would be no way to conceal it," social media watcher and journalist Wu Heng told Reuters.

Vaccine authorized

The latest H7N9 victim was from Anhui province, Xinhua reported. Among the new cases are several from Shanghai, Jiangsu and Zhejiang provinces, at least one of whom is dangerously ill, the news agency said.

The China Securities Journal reported on Wednesday that a vaccine for H7N9 has been authorized by China Food and Drug Administration and is expected to be introduced to the market in the first half of this year.

The exact source of infection remains unknown, although samples had tested positive in some birds in poultry markets that remain the focus of investigations by China and the U.N.'s Food and Agriculture Organisation (FAO).

The World Health Organization (WHO) said on Tuesday that it was looking into two suspected "family clusters" of people in China who may be infected with the H7N9 virus, potentially the first evidence of human-to-human spread.

The new virus is severe in most humans, leading to fears that if it becomes easily transmissible, it could cause a deadly influenza pandemic.

However, World Health Organisation (WHO) spokesman Gregory Hartl told a news briefing in Geneva that so far there is no firm evidence of human-to-human transmission occurring which could spark a pandemic. Chinese health authorities have said the same.