Taiwan officials announced a number of arrests in May

The man, Major Chuang Po-hsin, worked in electronic surveillance and was one of 17 officers and civilians arrested in an anti-spying sweep in May.

Taiwan says the alleged spy ring was discovered by accident, during investigations into credit card fraud.

Both Taiwan and its rival China are believed to run extensive intelligence networks in each other's territory.

TAIWAN-CHINA RELATIONS Ruled by separate governments since 1949 end of civil war China considers the island part of its territory China has offered a "one country, two systems" solution Most people in Taiwan support status quo Guide to Taiwan flashpoint

Both sides regularly announce the arrests and convictions of alleged spies.

The military court convicted Chuang of passing to China information his division had gathered about the mainland's military activities.

Defence officials have said the information he had access to was not highly confidential, but correspondents say that all such cases cause alarm in Taiwan.