Kim Jong Un has called for an "exponential" increase in North Korea's nuclear arsenal, including mass producing tactical nuclear weapons and developing new missiles for nuclear counterstrikes, state media said Sunday. In a report at the end of a key party meeting in Pyongyang, Kim said the country must "overwhelmingly beef up the military muscle" in 2023 in response to what it called US and South Korean hostility, the official KCNA reported. Claiming that Washington and Seoul were set on "isolating and stifling" the North, Kim said his country would focus on the "mass-producing of tactical nuclear weapons" and develop "another ICBM (intercontinental ballistic missile) system whose main mission is quick nuclear counterstrike". Such goals form the "main orientation" of the 2023 nuclear and defense strategy, the report said. Military tensions on the Korean peninsula rose sharply in 2022 as the North conducted sanctions-busting weapons tests nearly every month, including firing its most advanced ICBM ever. It capped the record-breaking year of launches by firing three short range ballistic missiles early Saturday, and conducting another rare late-night launch at 2:50 am (1750 GMT Saturday) on Sunday, Seoul's military said. The official KCNA reported Sunday that the launches had been "a test-fire of the super-large multiple rocket launchers." It said it was testing a new 600 mm super-large multiple rocket launcher capable of carrying nuclear weapons. In a separate KCNA report, Kim said the weapons put South Korea "as a whole within the range of strike and (were) capable of carrying (a) tactical nuclear warhead." North Korea was emphasizing this "in order to warn of the possibility of actual action", said Yang Moo-jin, professor at the University of North Korean Studies in Seoul. "North Korea is signaling a tactical shift of indirectly pressuring the United States by pressuring South Korea and escalating tensions on the Korean peninsula starting this year." The launches come just days after Seoul scrambled fighter jets as five North Korean drones made an incursion into the South's airspace Monday. But South Korea's President Yoon Suk-yeol said on Sunday that North Korea will continue to conduct constant nuclear and missile provocations, and the South's military should respond with clear retaliation, his office reported. During phone calls with military chiefs, he called for "solid mental readiness and practical training" to ensure any North Korean provocations will be met with retaliation, according to the statement from his office.