South Korean President Moon Jae-in has ordered his government to devise the “strongest” measures, including pushing for new sanctions, in response to North Korea’s sixth nuclear test, the Blue House announced on Sunday.

Moon convened a meeting of the National Security Council (NSC) from 1330 to 1500 KST.

“North Korea has conducted a more powerful nuclear test today than in the past while ignoring repeated warnings from us and the international community,” National Security Office (NSO) chief Chung Eui-yong said in a statement.

“The President ordered to draw up the strongest punitive measures in tandem with the international community against a series of provocations by North Korea including ICBM-class missile launch and nuclear test.”

The NSC has decided to “seek all possible diplomatic measures including the pursuit of UN Security Council sanctions resolution to make the North abandon its plan of nuclear weapon and missile in a complete, verifiable and irreversible way and completely isolate the North.”

The South will also conduct exercises to demonstrate its “military’s strike capabilities that disable the North’s nuclear facilities and missiles and have discussed “ways to deploy the most powerful strategic assets possessed by the U.S military in the perspective of the ROK – U.S. alliance.”

The presidential office declined to provide further information on what strategic assets would be deployed, but the statement does come amid increasing discussion in South Korea of the possibility of deploying U.S. tactical nuclear weapons to the peninsula.

In his statement to the NSC, President Moon said he was “disappointed and angry,” about the test, and urged North Korea to pursue dialogue with Seoul.

“North Korea made an absurd strategic mistake that will further accelerate its isolation in the international community by heightening tension on the Korean peninsula and also greatly threatening the world peace through a series of provocations,” the President said, in comments released by the Blue House.

“North Korea should declare to stop its plan to develop nuclear weapon and missiles as soon as possible and come forward to the path of a dialogue,” he added. “I once again emphasize that it is the only way to keep own safety and be guaranteed their future.”

Chung also held talks with his U.S. counterpart, Herbert McMaster, twice this afternoon, a Blue House statement added, before and after the meeting of the NSC to discuss the counter measures.

South Korea’s Joint Chiefs of Staff (JCS) also released a statement strongly condemning the test and promising “to punish provocations by North Korea and… show the powerful countermeasures of the ROK-U.S. Combined Forces in action.”

“As North Korea made an unscrupulous provocation despite our warning, we strongly warn that the responsibility can solely be placed on the North,” Maj. Gen. Cho Han-gyu, director of operations at the JCS, said, reporting on discussions between South Korea and U.S. military officials.

North Korea in a special broadcast at 1500 Pyongyang time confirmed the test as that of a hydrogen bomb designed to be used on an intercontinental ballistic missile (ICBM).

Announcer Ri Chun Hee read a statement from the Nuclear Weapons Institute of the DPRK regarding the “perfect success” of a “hydrogen bomb for intercontinental ballistic rocket.”

Meanwhile, China’s foreign ministry has said that it strongly condemns the test.

“We strongly urge the DPRK side to face up to the firm will of the international community on the denuclearization of the peninsula, abide by relevant resolutions of the UN Security Council, stop taking wrong actions that exacerbate the situation and are not in its own interest, and return to the track of resolving the issue through dialogue,” the statement, carried by CNN, read.

The announcement came after the state run Korean Central News Agency (KCNA) said on Sunday that the North has developed a hydrogen-bomb that can be loaded onto a new ICBM.

The test also comes less than a week after a test last Tuesday by North Korea of the Hwasong-12 missile, which flew over Japan and landed in the sea east of Japan.

In a call on Wednesday, Moon and Japanese Prime Minister Shinzo Abe discussed the possibility of a new United Nations Security Council (UNSC) sanctions resolution against the DPRK to increase pressure on North Korea.

Abe also met with UK Prime Minister Theresa May on Thursday, after which the two agreed to push for new UNSC measures against North Korea.

The UNSC most recently approved new international sanctions against Pyongyang on August 5 through resolution 2371.

Hailed as the toughest “in a generation” by U.S. Ambassador to the UN Nikki Haley, the resolution targets North Korea’s trade in coal, iron, lead and seafood, and are projected to reduce the value of the DPRK’s exports by a third if implemented correctly.

Featured image: Blue House