South Korea will take all measures to ensure that its citizens can return home safely from a troubled inter-Korean factory park in North Korea, an official said Thursday.

Presidential spokesman Jeong Yeon-guk made the comments as South Korea began to move its personnel out of the factory park in North Korea's western border city of Gaesong.

The factory park, the last-remaining symbol of inter-Korean economic cooperation, is home to more than 120 small South Korean plants that produce garments and other labor-intensive goods. More than 54,300 North Koreans work in the complex.

On Wednesday, South Korea announced that it has decided to completely shut down the industrial park in retaliation for North Korea's recent nuclear test and long-range rocket launch.

The shutdown "is an inevitable measure to make North Korea pay a price for its wrong behavior" and to prevent South Korea's resources from being used for North Korea's nuclear and missile programs," Prime Minister Hwang Kyo-ahn said in a Cabinet meeting.

The project has served as a major legitimate revenue source for North Korea. The South Korean firms annually provide about US$100 million in total to North Korea for their workers' income.

Hwang called on the foreign ministry to make efforts to make sure that the U.N. Security Council can slap strong and effective sanctions on North Korea for its nuclear and missile tests.

He also called on the defense ministry to maintain military readiness against any possible provocation from North Korea.

A North Korean patrol boat crossed the inter-Korean western maritime border on Monday before retreating back to the North's waters.

North Korea unilaterally closed the factory park in early 2013 in anger over South Korea-U.S. joint military exercises. But both sides resumed operation of the factory park later that year, as the North pledged not to shut it down again "under any circumstances." (Yonhap)