China's coronavirus outbreak has tested the limits of free speech on the country's heavily censored online and social media, with a brief window of liberalisation that opened during January subsequently slammed shut by authorities.

While censorship in China has tightened under President Xi Jinping, questions of transparency around the current outbreak are especially sensitive after Beijing's cover-up of the extent of the 2003 SARS epidemic fuelled suspicion and mistrust, and led to official calls for openness this time around.

The period from January 19 to February 1, when public concern about the coronavirus exploded just as China was gearing up for the Lunar New Year holiday, saw an uncharacteristic loosening.

Online buzz about the outbreak flourished, with netizens largely unfettered in criticising local authorities - but not central government leaders - over their handling of the crisis (file photo)

But censors have in the past week shutting down WeChat groups and scrubbing social media posts, according to Chinese reporters. Authorities have also reprimanded tech firms that gave free rein to online speech. Pictured, a cashier in a plastic gown works at the checkout of a supermarket in Wuhan, the epicenter of the novel coronavirus outbreak, on Monday

While censorship in China has tightened under President Xi Jinping, questions of transparency around the current outbreak are especially sensitive after Beijing's cover-up of the extent of the 2003 SARS epidemic fuelled mistrust. Pictured, a masked shopper wearing a plastic bag is seen outside a supermarket in Wuhan, the epicentre of the outbreak, on Monday

The new coronavirus has killed at least 1,018 people and infected more than 43,130 globally

Online buzz about the outbreak flourished, with netizens largely unfettered in criticising local authorities - but not central government leaders - over their handling of the crisis.

That liberalisation has come to end, with censors in the past week shutting down WeChat groups and scrubbing social media posts, according to Chinese reporters. Authorities have also reprimanded tech firms that gave free rein to online speech.

'Xi Jinping has made it clear that he expects efforts to strengthen "the guidance of public opinion" to be increased,' said Fergus Ryan, an analyst at the Australian Strategic Policy Institute (ASPI) who studies Chinese social media.

'We've already seen around 300 more journalists dispatched to Wuhan and surrounding areas to report on the outbreak. It's highly likely their brief is to paint a rosier picture of the government's relief efforts rather than engage in any muckraking or critical reporting.'

The cyberspace regulator, Cyberspace Administration of China (CAC), did not respond to phone calls or to requests for comment sent by fax.

Li Wenliang, 34, succumbed to the deadly contagion in the early hours of Friday morning local time, despite attempts to resuscitate him, the hospital which was treating him said. China's censorship machine was tested last week when the doctor died after catching the coronavirus

The medic caught the public's attention after he was reprimanded by police and accused of spreading 'fake news' for warning on social media of 'SARS at a Wuhan seafood market'. Pictured, mourners pay their respect to Li during a vigil ceremony in Hong Kong on Friday

China's censorship machine was tested last week when Li Wenliang, a Chinese doctor who had been reprimanded for issuing an early warning about coronavirus, died of the disease, triggering widespread outrage as well as mourning.

Online media outlets were permitted to report on Li's death, but not the anger it had engendered, and early discussions on social media calling for the Wuhan government to apologise to him later disappeared.

A notice sent to editors working for an online Chinese news outlet and seen by Reuters asked them not to 'comment or speculate' on Li's death, 'do not hashtag and let the topic gradually die out from the hot search list, and guard against harmful information.'

Online media outlets were permitted to report on Li's death, but not the anger it had engendered, and early discussions on social media calling for the Wuhan government to apologise to him later disappeared. Pictured, medical staff settle down a coronavirus patient after he moved into the isolation ward in a hospital in Wuhan, Hubei Province, on February 6

Last week, however, CAC announced that it had punished some websites, mobile applications and social media accounts for publishing illicit content on the outbreak, saying it wanted to foster a 'good online atmosphere' amid the country's efforts to contain the epidemic

Sarah Cook, the China media bulletin director at Freedom House, said that previous crises had also seen brief windows of openness, such as the deadly 2011 crash of a high-speed train and the devastating 2008 Sichuan earthquake, when domestic journalists and social media users felt emboldened.

'At the same time, initially, officials might be a bit flat-footed and distracted dealing with an unexpected crisis so things slip through the cracks. Even censors within some social media companies may be sympathetic to some of the content and let it through,' she said.

The brief window of media freedom came after officials in Wuhan, where the outbreak started, admitted that it was much worse than anticipated and were heavily criticised for their move in January to reprimand eight people for 'spreading rumours' on the emergence of the virus - one of whom was Li.

Chen Qiushi, a Chinese citizen journalist reporting from Wuhan, has been missing since 7pm local time Thursday when he said he was going to visit a makeshift coronavirus hospital

Mr Qiushi's mother has also posted a video on social media (pictured)

Last week, however, CAC announced that it had punished some websites, mobile applications and social media accounts for publishing illicit content on the outbreak, saying it wanted to foster a 'good online atmosphere' amid the country's efforts to contain the epidemic.

A notice circulated by CAC last week that was seen by Reuters asked audio and video platforms to step up control on 'harmful information and rumour' related to Wuhan virus.

It also asked them to stick to official media such as Xinhua and People's Daily, 'not to push any negative story, and not to conduct non-official livestreaming on the virus.'

Some investigative articles published by local media outlets from Wuhan have also been deleted.

Chen Qiushi, a citizen journalist who was sending dispatches from Wuhan over Twitter - which is blocked in China - including images of corpses in the city's hospitals, has been forcibly put under quarantine since Friday, according to his family and a friend managing his account in his absence.

Many Chinese Internet users have turned to black humour or shared images, songs and other art forms in private WeChat groups to express their dismay. One phrase widely shared mocked how many Internet pages and content were now showing 'server not found' or '404'.

'404+404+404+404+404=2020,' said the shared post.