Beijing (AFP) - The Chinese government has replaced its top envoy to Hong Kong, state media reported on Saturday, in the most significant personnel change since pro-democracy protests broke out in the city nearly seven months ago.

The removal of Wang Zhimin, the head of the Liaison Office which represents the central government in Hong Kong, comes as the city grapples with its biggest political crisis in decades.

"Wang Zhimin has been dismissed from his position as head of the Liaison Office" for Hong Kong affairs and was replaced by Luo Huining, state broadcaster CCTV said, without giving details.

Millions have come out for months on the streets in often-violent demonstrations demanding greater democratic freedoms in the semi-autonomous city in the strongest challenge yet to Beijing's rule since the return of the former British colony to Chinese rule in 1997.

Hong Kong is ruled under the "one country, two systems" principle, which gives the territory rights unseen on mainland China -- but protestors say are steadily being eroded.

Wang, 62, had been director of the liaison office since 2017.

In early December, following media reports that Beijing was considering replacing him, Wang vowed unwavering support to the Hong Kong's government and police force in a bid to quell the protests.