Story highlights

Seoul to limit access to the Kaesong Industrial Complex following North Korea's purported hydrogen bomb test

Opened in 2002, activity in the park has often halted or slowed due to tensions on the peninsula

Washington and Seoul discussing potential increased deployment of assets to South Korea following the test

CNN  — 

North Korean leader Kim Jong Un held a celebratory photo session in the wake of the country’s purported H-bomb test, as Seoul tightened control over a key symbol of inter-Korean cooperation.

On Monday, Kim invited dozens of soldiers, scientists and officials who worked on the test to the building of the Central Committee of the Workers’ Party of Korea (WPK), according to state news agency KCNA.

He said the assembled workers had “glorified the immortal exploits performed by President Kim Il Sung and leader Kim Jong Il” in carrying out the H-bomb test, which he described as “a great event to be specially recorded in the national history spanning 5,000 years.”

North Korean leader Kim Jong Un poses with workers who contributed to the H-bomb test, reports KCNA.

Earlier Monday, a spokesman for South Korea’s Unification Ministry, which deals with North Korean affairs, said that it would impose tougher entry restrictions to the Kaesong Industrial Complex and workers in the park would have their stays limited to the “minimum necessary level” for their own safety.

“This is an initial response measure to North Korea’s nuclear test,” Unification Ministry spokesman Jeong Joon-hee said.

“(The test) created tension and protecting the safety of our people became our priority.”

The move comes amid extremely heightened tensions on the Korean peninsula. Last week, South Korea resumed broadcasting propaganda across the Demilitarized Zone (DMZ) via loudspeakers following Pyongyang’s claim of a successful H-bomb test, which has been hotly disputed by its neighbors and the U.S.

Jeong said that Seoul believes North Korea will “respond to our loudspeaker broadcast,” but did not elaborate on what kind of response was expected.

Pyongyang considers the broadcasts tantamount to an act of war, and in the past has responded to them with artillery fire.

READ: CNN goes inside the Kaesong Industrial Complex

Rare symbol of inter-Korean cooperation

Situated north of the DMZ, the Kaesong complex was established in 2002 during the “Sunshine Policy” of South Korean President Kim Dae-jung, who sought better relations with Seoul’s northern neighbor.

Its creation allowed South Korean companies to benefit from the low cost of North Korean labor. Meanwhile, North Korea gained a valuable stream of hard currency revenue by appropriating an undisclosed amount of salary from its citizens working in Kaesong.

Activity in the park has often been halted or limited due to increased tensions on the peninsula.

In 2010, Seoul stopped all new investment in Kaesong, after accusing the North of torpedoing the navy ship Cheonan and killing 46 South Korean sailors – an allegation the North denied. Several months later, North Korea shelled South Korea’s Yeonyeong Island – killing four South Koreans – saying it had been provoked by Seoul’s annual military exercises.

North Korea pulled all its workers out for several months in 2013 amid tensions between the two countries.

Seoul and Pyongyang finally agreed to reopen Kaesong some five months later with an understanding that the industrial zone’s operations would no longer be “affected by political situations under any circumstances.”

Solidarity with Seoul

On Sunday, a U.S. B-52 bomber jet flew over Osan, South Korea in a show of solidarity with Seoul “in response to a recent nuclear test by North Korea”, according to United States Pacific Command.

The B-52 was flanked by South Korean F-15 fighter jets and U.S. F-16 fighter jets.

“This was a demonstration of the ironclad U.S. commitment to our allies in South Korea, in Japan, and to the defense of the American homeland,” said PACOM Commander Adm. Harry B. Harris Jr.

South Korea and the U.S. are also in discussions to potentially deploy additional strategic assets to the Korean peninsula, the South Korean Defense Ministry said.

“If they are to use the nuclear weapon, nuclear umbrella is the response against it. And you can view the deployment of B-52 as one of the means of nuclear umbrella,” said Kim Min-seok, South Korean Defense Ministry spokesman.

More than 28,000 U.S. troops are based in South Korea, according to the State Department.

CNN in North Korea

The only U.S. broadcaster currently operating in the tightly closed country, CNN has been given exclusive access to North Korean sites and prisoners.

On Sunday, CNN’s Will Ripley spoke to jailed Canadian pastor Hyeon Soo Lim, under the close watch of his North Korean guards.

Lim said that he longed to see his family again, and hoped “I can go home some day.”

Last week, the CNN crew visited the North Korean Science and Technology Center, the public face of the government’s push to develop its technological and scientific capabilities as it ramps up its nuclear program.

The center, opened on January 1 by Kim Jong Un, is centered around a replica of the 2012 rocket that launched North Korea’s first and only satellite into orbit. Government minders said that the center showed how much of a “priority” science was for the country.

CNN’s Will Ripley and Holly Yan contributed to this report.