Beijing's liaison office in Hong Kong has voiced its "resolute support" for the conviction of former media tycoon Jimmy Lai, saying his offences have left society with "excruciating pain".

In a statement on Monday, an office spokesperson said evidence presented in court showed the Apple Daily founder was the "mastermind" and "financier" of anti-China forces in Hong Kong, and that he was willing to act as a pawn of external forces that wished to use the city to contain the country.

Lai had long manipulated anti-China individuals and organisations such as Apple Daily and colluded with anti-China forces abroad, the office said, adding that the former businessman spread "unscrupulous statements" intending to incite others to subvert the SAR regime.

"[He] even directly organised resistance movements, begged external forces to impose sanctions on China and Hong Kong, and did not stop after the implementation of the National Security Law," the office said.

"His crimes have caused serious harm to Hong Kong's society and left excruciating pain on Hong Kong people."