Underground nuclear weapons testing

South Korea warned Tuesday North Korea that using its nuclear weapons would put it on a "path of self-destruction," in unusually harsh language that came days after North Korea legislated a new law that would allow it to use its nuclear weapons preemptively.

North Korea has passed a law declaring its readiness to launch preventive nuclear strikes, including in the face of conventional attacks, state media said on Sept. 9. 

The move effectively eliminates the possibility of denuclearisation talks, with leader Kim Jong Un saying the country's status as a nuclear state was now "irreversible".

U.S. Deputy Secretary of State Wendy Sherman on Tuesday warned of a forceful response if North Korea carries out its first nuclear test explosion in nearly five years as she traveled to Seoul to meet with South Korean and Japanese allies and discuss the escalating standoff.

North Korea has test-fired a new type of tactical guided weapon designed to boost its nuclear fighting capability, state media reported Sunday, a day before its chief rivals the United States and South Korea begin annual military drills that the North views as an invasion rehearsal.

North Korea said on Sept. 28 it successfully tested a new hypersonic missile it implied was being developed as nuclear capable, as it continues to expand its military capabilities and pressure Washington and Seoul over long-stalled negotiations over its nuclear weapons.

North Korea test-fired a new "long-range cruise missile" over the weekend, state media reported on Sept. 13, with the United States saying the nuclear-armed country was threatening its neighbors and beyond.

Pictures in the Rodong Sinmun newspaper showed a missile exiting one of five tubes on a launch vehicle in a ball of flame, and a missile in horizontal flight.

U.N. experts say North Korea has increased imports and exports of banned and restricted goods such as coal and petroleum products as it continues to enhance its illicit nuclear and ballistic missile programs in violation of sanctions.

North Korea's test of a new missile is meant as a "solemn warning" over rival South Korea's weapons development and plans to hold military drills with the United States, Pyongyang said on July 26 as it continued its pressure campaign ahead of potential nuclear talks.

North Korea is considering suspending talks with the United States and may rethink a ban on missile and nuclear tests unless Washington makes concessions, news reports from the North's capital on March 15 quoted a senior diplomat as saying.

Japan Times - North Korea announced Saturday that it had suspended nuclear and longer-range missile tests and shut down its main nuclear test site as the sanctions-hit country seeks to shift its focus to shoring up its moribund economy, state media said, less than a week ahead of a key inter-Korean summit.