UPDATE: 3:28 a.m. EST — China, the biggest supporter of North Korea, urged Thursday all concerned parties to exercise restraint, after the Kim Jong Un-led regime fired two short-range missiles into the East Sea, which lies between the two Koreas and Japan. 

China's foreign ministry spokesman Hong Lei described the current situation as “highly sensitive,” and said all the “relevant parties” should avoid escalating tensions on the Korean peninsula, South Korea's Yonhap News Agency reported.

Original story:

North Korean leader Kim Jong Un has called for production of more nuclear material by operating the country's nuclear facilities normally, and also increasing the production of highly precise and miniaturized nuclear weapons, despite international criticism of the reclusive regime over such moves, Uriminzokkiri, a state-run website reported Thursday, according to KCNA Watch. The latest announcement from North Korea comes as it also said Thursday it will nullify all cross-border agreements on economic cooperation with South Korea and liquidate South Korean assets in the North.

Kim met with North Korean nuclear weapons scientists and technicians to provide guidance over boosting the nuclear arsenal in the country. He reportedly praised the scientists for their success in the field and called the miniaturization of nuclear warheads to fit ballistic missiles a “true nuclear deterrent.” He also said that the Workers' Party of Korea is focused on working on two fronts — boosting the country’s defense capabilities and developing deterrents.

“The right to pre-emptive nuclear strike is by no means a monopoly of the US, he (Kim) said, declaring that if the US imperialists infringe upon our sovereignty and right to existence with nuclear weapons, we will never hesitate to deliver a preemptive nuclear strike at them,” the report by Uriminzokkiri said, adding: “He called on the nuclear scientists to massively produce nuclear materials through normal operation of nuclear facilities on a high level and increase the production of more powerful, highly precise and minimized nuclear weapons and their carriers and upgrade the already deployed means of nuclear strike without interruption by incessantly developing the nuclear weapon technology.”

Pyongyang’s decision to nullify all cross-border economic cooperation agreements with Seoul comes as a response to the new sanctions slapped by South Korea Tuesday over the North’s latest nuclear test and a long-range rocket launch, Yonhap reported Thursday. The sanctions included a ban on shipping vessels that stop at any North Korean port, and blacklisting several individuals and entities. South Korea’s punitive punishment followed the resolution adopted by United Nations Security Council last week that approved tougher sanctions against the reclusive North.

“From this moment, we will view all agreements which the two Koreas have made on economic cooperation and exchanges as invalid,” a spokesman who handles the inter-Korean affairs for North Korea, said, according to Yonhap. The country’s decision to sell all assets owned by South Korean companies in North Korea after Seoul announced that it will suspend an inter-Korean tourism project at Mount Kumgang and close the Kaesong Industrial Complex, a joint industrial park in the North. Following Kaesong’s closure, Pyongyang expelled South Korean nationals living there and designated the complex as a military-controlled area.

Early Thursday, North Korea also fired two-short range missiles into the East Sea — which lies between Japan and the two Koreas — as a display of its protest against the largest-ever annual joint military drills between South Korea and the U.S.

Japan’s Chief Cabinet Secretary Yoshihide Suga said Thursday, according to Reuters, that Tokyo continues to remain vigilant and prepared for all circumstances, and also urged North Korea to refrain from taking provocative actions in the region.