Whistleblowers who sounded the alarm about the coronavirus in China were reportedly arrested for 'spreading rumours'.

A leading UK expert on China has claimed that the whistleblowers had warned about the deadly virus a month ago.

The revelation comes as health officials declare a global emergency over the rapidly spreading coronavirus.

laboratory assistant prepares a test for the Coronavirus at the Amedeo di Savoia hospital in Turin, Italy on January 30

French citizens arrive and settle aboard of an evacuation plane with destination southeastern France, before departure from Wuhan Airport (WUH), China, on January 30

The nationwide death toll in China's coronavirus outbreak has risen to 213, with nearly 2,000 new cases confirmed, the National Health Commission said on Friday.

In its daily update, the commission said 43 new deaths had occurred as a result of the virus, all but one of them in hardest-hit Hubei province where the virus first emerged.

Dr Yukteshwar Kumar of the University of Bath told the Mirror that those who tried to warn about the virus were allegedly silenced by the state.

He claims that the spread of the virus could have been reduced if people were made aware of the outbreak in late December.

'They were asked to sign a confession stating that they will not spread false news. If they had taken steps earlier the situation could have been better because they did know about it,' Dr Kumar told the publication.

Workers produce protective masks at a factory in Nonthaburi province, on the outskirts of Bangkok, Thailand, January 30

The virus has been confirmed in more than 15 other countries across the globe

'People could have been made aware in late December. The authorities could have stopped people travelling earlier.

'I highly appreciate the efforts made by the government of China in locking down the whole city. However, if they'd listened to the advice of these eight people and some scientists the situation would have been perhaps better.'

A legal document obtained by Dr Kumar reportedly appears to be signed and finger-printed by citizens promising not to discuss the outbreak.

A man wears a masks in Chinatown following the outbreak of the novel coronavirus, in Chicago, Illinois, January 30

The WHO had initially downplayed the threat posed by the disease, but revised its risk assessment after crisis talks on Thursday.

'We must all act together now to limit further spread... We can only stop it together,' WHO chief Tedros Adhanom Ghebreyesus told a briefing in Geneva.

Tedros nevertheless said travel and trade restrictions with China were unnecessary to stem the spread of the virus, which has now been confirmed in more than 15 other countries across the globe.

Many countries have already urged their citizens not to visit China while some have banned entry for travellers from the central Chinese city of Wuhan, where the virus first surfaced.