The men, who were arrested in January, earlier denied they were recruiting spies for China. They both face up to five years in jail if convicted.

Taiwan on Thursday charged two former state officials with violating the national security law by organising meetings between former senior military officers and Chinese intelligence personnel in order to set up an espionage network for China.

The Kaohsiung District Prosecutor’s Office said the two officials “made it possible for Chinese intelligence personnel to establish contact with our retired generals and even recruit them to create a network of Chinese organistions through their actions.”

It noted that retired naval officer Hsia Fu-hsiang and former lawmaker Lo Chih-ming have worked with Chinese organisations since 2013 to “promote (Taiwan’s) reunification with China” by recruiting retired generals.

According to prosecutors, the pair established relationships with at least 48 senior retired officers and arranged 13 paid trips for them from 2013 to 2018.

China claims self-ruled Taiwan as part of its territory and has vowed to bring the island under its control one day, by force if necessary.

Taiwan's strongest ally the United States warned in October that China is pursuing unification at a much faster timeline. At around the same time, Chinese leader Xi Jinping embarked on a historic third term as head of both the Communist Party and the military.

Both China and Taiwan have been spying on each other since the end of a civil war in 1949 that saw nationalists fleeing and settling in Taiwan while the Communist Party take control of the mainland.

"We urge retired military officers to be cautious about fraudulent patments when they go to events in China to avoid falling into the traps" of China, prosecutors said.

The case comes shortly after prosecutors opened an investigation into a retired air force colonel suspected of recruiting at least six active-duty Taiwanese air force and naval officers on behalf of China over an eight-year period.

Some former high-ranking Taiwanese military officials have in recent years been accused of aiding Chinese intelligence by developing espionage networks for China.

A retired air force major general was found guilty in January of accepting meals and trips from a Hong Kong businessman who was acting on China's behalf. He was given a four-year prison sentence that was suspended because he showed remorse and had no previous criminal record.