China's ruling Communist Party leaders have congratulated themselves on their "extremely extraordinary" success in handling the Covid-19 outbreak domestically, ahead of a World Health Organization probe into the disease's origins.

China faced a barrage of criticism at home and abroad over its initial handling of the virus, which emerged in the central city of Wuhan last December.

China's Politburo, the top decision-making body of the Communist Party, said late Friday that the party leadership "played a decisive role in leading ... China in prevailing over the rare risks and challenges this year."

"At the critical moment ... the Party Central Committee took a long-term view ...achieving an extremely extraordinary glory in this extremely unusual year," state news agency Xinhua reported, citing a statement issued after the two-day meeting.

China has largely curbed the spread of the virus, and was one of the only major economies to report growth this year. But it has been accused of covering up the initial outbreak, and so contributing to the virus' spread internationally.

At home, Beijing has attempted to stifle criticism by punishing at least eight whistleblowers.

A Chinese citizen journalist who reported on Wuhan's outbreak, Zhang Zhan, has been detained since May and is expected to go on trial on Monday.

Zhang is a former lawyer who travelled to the city in February to report on the chaotic initial stages of the outbreak, through livestreams and critical essays widely shared on social media platforms banned in China.

The two-day Politburo meeting comes shortly before an international team of WHO experts is expected to arrive in China to investigate the animal origins of Covid-19, during which trip they will visit Wuhan.

An expert from the team told AFP this week that the investigation was "not about finding a guilty country or a guilty authority", but about "about understanding what happened to avoid that in the future".

Beijing has recently attempted to cast doubts on the origins of the virus -- the state-run People's Daily newspaper said in a Facebook post in early November that "all available evidence suggests that the coronavirus did not start in central China's Wuhan".

China has also tried to enhance its soft power push during the pandemic -- promising to share its vaccines with developing countries, and engaging in “mask diplomacy" -- donating personal protective gear to countries in need.