A North Korean defector has been arrested for selling classified intelligence about the South Korean military to a foreign agent, prosecutors said Wednesday.

The suspect, only identified by the surname Lee, was charged with violating the Military Secret Protection Act, the Seoul Central District Prosecutors' Office said.

Lee allegedly obtained the highly sensitive information from former ranking officials at the Korea Defense Intelligence Command under the Ministry of National Defense, and handed it over to an agent working at a diplomatic mission of an East Asian country. Prosecutors did not identify the country involved. 

Prosecutors discovered Lee's involvement while they were digging into the espionage case involving the former KDIC officials. They were indicted on espionage charges last month.

Prosecutors said 109 pieces of classified military information were leaked, including personal details of South Korean spies working at overseas missions. They returned home immediately after the incident was discovered.

Prosecutors said they are expanding the probe to determine if there were any others involved.  (Yonhap)