Chinese health authorities have warned the coronavirus' ability to spread is getting stronger and infection rates could continue to rise.
It comes as the death toll in China from the outbreak rises to 80.
The central Chinese province of Hubei - where the respiratory virus is thought to have originated - has been isolated in a bid to slow its spread, and in the provincial capital of Wuhan, the use of non-essential vehicles has been banned.
Outside the epicentre, Shandong province, Beijing, Shanghai, Xi'an and Tianjin have announced bans on long-distance buses entering or leaving.
In the provinces of Guangdong and Jiangxi it is now mandatory for residents to wear face masks in public.
China's Health Minister Ma Xiaowei said it is not clear how easily the virus spreads between people.
"The ability of the virus to spread seems to be getting stronger," he said.
"We need more clinical data to analyse its toxicity.
"The quickening spread of the epidemic has brought extra challenges and pressure to the work of prevention and control.
"Experts have assessed that the epidemic has entered a grave and complicated stage."
He said while the virus is not as powerful as SARS, it is still too early to know the risk of it mutating.
China's Health Commission Minister Ma Xiaowei at a press conference in Beijing about the outbreak of the coronavirus Source: Yomiuri Shimbun
"The growth of the epidemic is accelerating," he said.
"I'm afraid it will last for a period of time. It is possible for us to see a continuous increase in the number of cases in the near future."
Health authorities in New South Wales are expected to confirm Australia's fifth case of the virus today.
Three patients in New South Wales and one in Victoria have already been diagnosed.
New South Wales Health Minister Brad Hazzard said it is important Chinese travellers to Australia are aware of the virus' flu-like symptoms.
"I am concerned that there has been some information that is circulating on WeChat and other social media platforms that aren't entirely accurate," he said.
"I would stress that there are no centres here in Sydney, or no centres across New South Wales, where this particular virus has been located.
"The critical issue is where you have come from.
"If you have come from Wuhan or Hubei then you should be alert."
Chief Medical Officer Brendan Murphy said the risk of infected people coming to Australia is lower than before thanks to China's widespread lockdown.
Australia is working to keep out the deadly coronavirus, as flights from China arrive in the country Source: AAP
"However, because people could have left the province before the lockdown and could come to Australia via a number of flights, we are now meeting every flight from China and providing the passengers with an information sheet," he said.
