South Korean military authorities said Saturday they were investigating the online leak of the personal information of thousands of retired army special forces troops.

Private information of 3,664 former special forces troops -- their Web IDs, names, phone numbers, e-mail addresses and the units they served -- was leaked from a Web site of their fraternity organization, military investigators said.

Also leaked were the personal details of two active-duty special-warfare officers who subscribed into the Web site, they said.

"We confirmed their personal information was leaked on Google and deleted it today," a military investigator said on the condition of anonymity.

Military officials said they were investigating whether the leak was a result of hacking.

South Korea, one of the world's most wired nations, has concerned about cyber attacks from North Korea.

For years, Seoul blamed Pyongyang for launching cyber attacks on its government and private Web sites. In May, South Korea accused the North of staging a cyber attack that disrupted operations at one of its largest banks.

North Korea has denied the accusations. (Yonhap News)