Beijing claims self-ruled Taiwan as its territory and has ramped up military and political pressure on the island in recent years.

The two sides split in 1949 after a civil war and have been spying on each other ever since.

The pair were "induced by" China to collect "confidential defence documents" since 2019 and "recruit active servicemen to develop an organisation" in return for hefty fees, Taiwan High Court's Tainan branch said.

Huang Lung-lung and his son Huang Sheng-yu, businessmen formerly based in China, were found guilty of bribing two servicemen from an air defence and missile battalion to pass on confidential military information, it said in a statement.

The court also sentenced the servicemen, a lieutenant and a sergeant, to seven and six years in prison, respectively. It did not elaborate on the kind of information that was leaked.

It said the Huangs "disregarded national security" to spy for China and that the NT$1.7 million ($52,160) they were paid for it had been confiscated.

The pair remained free pending a potential appeal against the ruling.

Tuesday's sentencing was the latest in a recent string of spying cases on the island.

Ten soldiers were indicted in November for allegedly spying for China, including two who made a video pledging to "surrender" to the Chinese military.

A retired air force colonel was sentenced to 20 years in prison in October for spying for Beijing and handing over confidential national security information.