SHANGHAI (REUTERS) - The death toll in China from a new strain of bird flu rose to nine on Tuesday, said state media, who also quoted Chinese authorities saying a vaccine should be ready within months.

The latest victim was from Anhui province, the official Xinhua news service reported.

The H7N9 strain, which was confirmed in humans for the first time last month, has now infected 28 people, all of them in eastern China, of whom nine have died, according to data from the National Health and Family Planning Commission cited in the Xinhua report.

The cases include another four people confirmed to be infected with the virus, two in Shanghai and two in Zhejiang province, one of whom was dangerously ill, according to Xinhua.

The China Securities Journal reported on Wednesday that a vaccine for H7N9 has been authorised 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 UN'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, and Chinese health authorities have said the same.