Chinese mainland confirmed 440 cases of pneumonia caused by a new coronavirus by Tuesday midnight, affecting 13 provinces, with the death toll rising to nine, the National Health Commission said on Wednesday morning.

Overseas, five cases have been reported -- three in Thailand and one each in South Korea and Japan.

The number of confirmed cases in Chinese mainland rose from 291 reported earlier on Tuesday by the commission.

Three new deaths, all occurring in Hubei province, were reported on Tuesday. The outbreak first emerged in Hubei's Wuhan city in late December.

Authorities have traced 2,197 people who have had close contacts with the infected patients, and 765 of them have been moved out of quarantine.

Li Bin, deputy director of the commission, said there have been instances of human-to-human transmission and infections among medical workers. Some transmission across neighborhoods has also been reported.

"The virus is likely to mutate and the risk of further spread of the disease remains," he said.