A local court sentenced an executive of a South Korean defense company to four years in prison Thursday for leaking military secrets to more than two dozen domestic and foreign firms.

Last July, the 52-year-old executive, identified only by his surname Kim, was indicted on charges of collecting classified military documents and passing them on to 25 companies at home and abroad between 2008 and June last year.

The leaked documents contained information about some 31 defense enhancement projects, including a government plan to build 20 next-generation frigates by 2020.

The Seoul Central District Court said in its ruling that Kim deserved heavy punishment for his actions.

"Kim acted only for his own benefit and disclosed government secrets so recklessly," Judge Jo Yong-hyeon said. "Because the leak was so massive, there's even a possibility that the information could end up in the hands of our enemies."

Three other men, two of whom belong to the same company as Kim's and are former military officers, also received sentences ranging up to a year and a half in jail with a three-year stay of execution.

They were all charged with colluding with Kim to collect secrets and leaking them to interested companies. (Yonhap)