Taiwan (search) has arrested 17 military officers and civilians on suspicion of passing secrets about the island's intelligence capability to rival China (search), the island's military said Wednesday.

Senior officers said the alleged spies leaked details of what the Taiwanese military knows about Chinese military exercises.

A Ministry of National Defense (search) statement identified the key figure in the alleged spy ring as Maj. Chuang Poh-hsing, who worked in a unit of the ministry's electronic information department that handles sensitive missile systems data. No missile secrets were leaked, the ministry said.

"The documents he leaked included information about annual military exercises by China's navy and air force... but no missile, radar, or secret information codes," Lt. Gen. Li Hsiang-chou (search), the department's chief, told reporters.

The information about China's exercises would be of interest to Beijing because it could indicate what Taiwan knew about China's military capabilities, the military said.

Chuang was believed to have had no access to the department's most sensitive information because he had been employed there for only one year at a low security level, Li said. Chuang worked at the department's office in the Taipei suburb of Linkou.

He allegedly passed the stolen information to a retired officer, Huang Yao-chung (search), the ministry said. Huang was among those arrested Tuesday.

Investigators said they uncovered the ring after the coast guard found that a suspect arrested last September for smuggling guns and drugs was also involved in making false credit cards — and passing confidential information to China.

The leader of the credit card forgers, Su Tung-hung, was among the other suspects arrested Tuesday, when more than 200 investigators searched 20 locations and found dozens of secret documents. They also found more than $3 million worth of machinery used to produce fake cards, the Ministry of Justice (search) said.

Taiwan and China frequently announce the arrest and conviction of alleged spies and are believed to be running extensive spy networks on each other's territory. Taiwan's defense ministry said Wednesday it would tighten security to thwart spying by Beijing.

The sides split at the end of a civil war more than five decades ago. Beijing still threatens military force should the island move toward declaring formal independence.