There is no reason to modify Hong Kong's "one country, two systems" model of administration, Chinese President Xi Jinping stated during an unusual visit to the financial hub on Friday after John Lee was sworn in as the city's new leader.

All leaders, particularly Xi, wore masks and stood at least one metre apart during the inauguration rituals. There was no handshake.

Near the convention center, red lamps and posters proclaiming a "new age" of stability adorned major highways and sidewalks.

This is Xi's first trip to Hong Kong since 2017, when he inaugurated the city's first female leader, Carrie Lam, who presided over some of the territory's most turbulent moments, including anti-government protests in 2019 and the COVID outbreak.

Former security chief Lee, who is sanctioned by the United States for his part in enacting the security law, assumes command at a time when the city is witnessing an outflow of people and talent due to some of the world's strictest COVID-19 limitations.

The United Kingdom surrendered Hong Kong to Chinese control on July 1, 1997, with Beijing guaranteeing extensive autonomy, unrestricted individual rights, and judicial independence until at least 2047.

China's critics, particularly Western nations, accuse authorities of trampling on these liberties with a comprehensive national security ordinance imposed by Beijing on the city in 2020 in the wake of massive pro-democracy demonstrations the previous year.

China and Hong Kong deny the allegations, claiming that the law "established order from instability" in order for the city to flourish.

Xi asserted that the security law was advantageous for the "democratic rights" of the city's citizens and that the "one country, two systems" formula would be maintained.

The authorities assembled a vast security force, shutting roads and airspace surrounding Victoria Harbour, where the final British governor, Chris Patten, returned Hong Kong to China in a rain-soaked ceremony in 1997.

Friday's annual flag-raising ceremonies were missed by Xi, who, according to media reports, spent the night in Shenzhen after arriving in Hong Kong on Thursday.

Five years ago, Xi spent the entirety of his trip in Hong Kong. This time, neither his overnight location nor the reasons he may have selected Shenzhen have been publicly confirmed.

On Thursday, Hong Kong registered more than 2,000 daily COVID incidents, a number that would result in extremely stringent restrictions in any mainland city. China is the only big nation that chooses to eradicate any outbreak at whatever cost as soon as it happens.