The statement, released through the North’s state media, came at about the same time that a group of defense analysts, after studying recent satellite images, said they had detected new vehicles, mining carts and other signs of activity at the Punggye-ri underground nuclear test site in northeast North Korea.
”Such activity, coming shortly after the largest underground nuclear test conducted at Punggye-ri to date (via the North Portal), suggests that on-site work could now be changing focus to further prepare those other portals for future underground nuclear testing,” the defense analysts, Frank V. Pabian, Joseph S. Bermudez Jr. and Jack Liu, said in a Tuesday report on 38 North, a website focused on North Korea. The analysts gave no indication that a test appeared to be imminent.
The analysts also said that the explosive yield from the Sept. 3 nuclear test may have been as much as 250 kilotons, based on revised estimates of the magnitude of the tremor created by the blast. That would be much higher than most official estimates, which have varied. Japan, for example, gave an estimate of 160 kilotons, while South Korea’s was as low as 50 kilotons.
The analysts said the data appeared to verify the North’s claim that it had detonated a hydrogen bomb, a much more powerful device than the atomic bombs it detonated in its early tests. The United States, South Korea and other governments have yet to confirm that the North tested such a weapon, but the Sept. 3 test, the North’s sixth, was by far its most powerful to date. Satellite imagery since the test has showed evidence of numerous landslides at the test site.
On Wednesday, South Korea’s Nuclear Safety and Security Commission said it had detected traces of radioactive xenon gas from the nuclear test. But the data was not sufficient to determine what type of nuclear device the North had detonated, it said.
The latest United Nations sanctions against the North were considerably weaker than what the United States had sought. Among other things, the Trump administration wanted a complete cutoff of oil exports to the North.
“We think it’s just another very small step — not a big deal,” President Trump said of the new sanctions on Tuesday. “But those sanctions are nothing compared to what ultimately will have to happen.”
In the past week, Mexico and Peru have decided to expel North Korean ambassadors to protest the country’s continued violation of United Nations sanctions. South Korea’s foreign minister, Kang Kyung-wha, said Tuesday that a Middle Eastern country, which he did not identify, had also agreed to expel Pyongyang’s envoy.
North Korea’s ambassador to Peru, Kim Hak-chol, said Tuesday that his expulsion “throws gasoline on the fire,” according to Reuters.
On Wednesday, the South Korean military said it had successfully tested a new air-to-land “bunker buster” Taurus cruise missile, part of its effort to increase its ability to destroy key weapons sites and bunkers deep underground where the North’s leaders might take refuge.
South Korea has agreed to buy 260 Taurus missiles from Taurus Systems, a German and Swedish joint venture. The missiles are among billions of dollars’ worth of new weapons that South Korea is buying to strengthen its pre-emptive and retaliatory strike capabilities as a deterrent against North Korea.
They have a maximum range of 310 miles, meaning that South Korean planes can launch them without entering North Korean airspace. They can also fly a low, terrain-hugging route to better avoid radar, defense officials said.
North Korea flew an intermediate-range missile over northern Japan last month and has threatened to launch more missiles into the Pacific.