The personal information of nearly 1,000 North Koreans who defected to South Korea has been leaked after unknown hackers got access to a resettlement agency's database, the South Korean Unification Ministry said on Friday.

The ministry said it discovered last week that the names, birth dates and addresses of 997 defectors had been stolen through a computer infected with malicious software at an agency called the Hana center, in the southern city of Gumi.

"The malware was planted through emails sent by an internal address," a ministry official told reporters on condition of anonymity, due to the sensitivity of the issue, referring to a Hana center email account.