Countries including the United States, Britain and Australia have spoken out against Monday's sentence, with US Secretary of State Marco Rubio calling it "unjust and tragic".

The European Union said it "deplores" 78-year-old Lai's sentencing and called for his "immediate and unconditional release", while Britain vowed to "rapidly engage further" on his case.

Asked about the criticism on Tuesday, China's foreign ministry said that "certain countries and institutions have used this judicial case... to maliciously smear Hong Kong".

"China firmly opposes this and has lodged solemn representations with the relevant countries and institutions," spokesman Lin Jian said at a regular news briefing.

Lai, a British citizen and founder of the now-defunct Apple Daily newspaper, was found guilty in December of collusion with foreign countries by urging them to impose sanctions on Hong Kong and for publishing "seditious" articles in his paper.

His sentence is by far the harshest under Hong Kong's national security law, which Beijing imposed in 2020 after huge and sometimes violent pro-democracy protests in the former British colony.

Lin said the ruling was "based on facts and law, is legal, just and beyond reproach".

Beijing urged "relevant parties to... immediately cease meddling in Hong Kong matters and China's internal affairs in any way", he added.