China said on Friday it had sentenced a British national in 2022 to five years in jail for spying, in its official confirmation of a case that had gone unreported until this week.

The Wall Street Journal first broke news of the case of UK businessman Ian Stones on Thursday, reporting, citing his family and other sources, that he had disappeared in 2018 after decades of work in China.

Asked about the report on Friday, foreign ministry spokesman Wang Wenbin said a Beijing court in 2022 "sentenced in first instance the British defendant... to five years in prison for the crime of illegally obtaining intelligence for overseas actors".

After an appeal, he added, the case was upheld in September last year.

Wang, referring to Stones by a Chinese name, said the "court tried the case strictly in accordance with the law".

Beijing, he said, "fully guaranteed the various legitimate rights" of the prisoner and had arranged for UK officials to visit him and attend his trial.

"China is a country governed by the rule of law," Wang said.

"The judicial organs strictly promote the handling of cases in accordance with the law, safeguarding the rights and legitimate interests of both Chinese nationals and foreigners," he added.

China and Britain have traded barbs in recent months over allegations of perceived espionage and its resulting impact on national security.

This month, Beijing said the head of a foreign consultancy had been found to be spying for Britain's MI6 intelligence service.

The Ministry of State Security said in a WeChat post that Britain's Secret Intelligence Service -- also known as MI6 -- used a foreign national with the surname Huang to establish an "intelligence cooperation relationship".

And Britain has in turn warned that Chinese spies are increasingly targeting officials, allegations that Beijing has denied.

A researcher at the British parliament was arrested last year under the Official Secrets Act and subsequently denied spying for Beijing.

Spy games 

China, which has a broad definition of state secrets, has publicised several other alleged spying cases.

In May, authorities sentenced 78-year-old American citizen John Shing-wan Leung to life in prison for espionage.

And in October, the MSS published the story of another alleged spy, surnamed Hou, who was accused of sending several secret and classified documents to the US.

China last year also conducted raids on a string of big-name consulting, research and due diligence firms.

Last May, China said it had raided the offices of US consultancy firm Capvision in order to safeguard its "national security and development interests".

Beijing also questioned staff at the Shanghai branch of another American consultancy, Bain, in April.

And authorities detained workers and shuttered a Beijing office belonging to US-based due diligence firm Mintz Group in March.

The US government and its chambers of commerce warned that the raids damage investor confidence and the operations of foreign businesses in China.