North Korea fired a ballistic missile into the sea off the coast of South Korea on Monday, the South Korean military said, according to The Associated Press . The military said in a statement only that the launch was made Monday morning local time, without giving further details. The launch is the second one over the past day. Hours earlier, South Korea reported that North Korea conducted a short-range ballistic missile test into the sea in a resumption of its weapons testing activities. Observers said the North’s back-to-back launches were likely a protest against the moves by South Korea and the United States to bolster their nuclear deterrence plans. North Korea tested dozens of ballistic weapons in 2022, including its first intercontinental ballistic missiles since 2017. In July, North Korea test-fired a Hwasong-18 solid-fuel intercontinental ballistic missile (ICBM), in a launch that was supervised by Kim. Related articles: North Korean leader urges expansion of nuclear capabilities Russia-North Korea defense pact goes into effect Trump mulling direct talks with Kim Jong Un 'Korean peninsula facing an unprecedented risk of nuclear war' In September, North Korea announced it had built a "tactical nuclear attack submarine" as part of its effort to strengthen its naval force. That announcement came days after the country said it staged a "simulated tactical nuclear attack" drill with mock atomic warheads attached to two long-range cruise missiles that were test-fired into the ocean.