SEOUL • The United Nations nuclear watchdog's chief has said North Korea's sixth nuclear test conducted earlier this month showed the isolated country has made rapid progress on weapons development that posed a new global threat.
Tensions on the Korean peninsula have increased markedly since the test, which led to a new round of sanctions against the North after a unanimous UN Security Council resolution.
"(The) yield is much bigger than the previous test, and it means North Korea made very rapid progress," International Atomic Energy Agency (IAEA) director Yukiya Amano told reporters in Seoul yesterday.
"Combined with other elements, this is a new threat and this is a global threat," he said, after a meeting with South Korean Foreign Minister Kang Kyung Wha.
Mr Amano said the IAEA did not have the capacity to determine whether the North had tested a hydrogen bomb, as Pyongyang has claimed.
Tensions had already flared after North Korea tested two more intercontinental ballistic missiles and other launches as it pursues its nuclear and missile programmes in defiance of international pressure.
South Korea said on Thursday that the North could engage in more provocations near the anniversary of the founding of the North Korean communist party and China's all-important Communist Party Congress.
Japanese Defence Minister Itsunori Onodera yesterday also urged caution that Oct 10, the start of Lower House election campaigns in Japan, coincides with the celebration of the founding of the North Korean communist party.
North Korea has often marked significant events on its calendar by conducting weapons tests.
Insults and threats hurled between North Korean leader Kim Jong Un and United States President Donald Trump have aggravated the situation further.
Members of the international community have urged both countries to resolve matters peacefully while boosting pressure on Pyongyang to curb its weapons programmes.
A US State Department official said on Thursday that China was making progress in enforcing sanctions imposed on North Korea and urged sceptical members of Congress not to rush to enact new measures before giving Beijing's efforts a chance to take effect.
Meanwhile, a study by researchers at Middlebury College's James Martin Centre for Non-Proliferation Studies suggests that North Korea has mastered the production of a specialised rocket fuel known as UDMH, which is used in the long-range missile launches that have escalated tensions between North Korea and the US.
Though North Korea may have previously relied on foreign assistance in obtaining or making the fuel, as some analysts believe, it no longer appears to need the help.
If they are not dependent on foreign suppliers, said Professor Vipin Narang, who studies nuclear issues at Massachusetts Institute of Technology, then "even the most targeted sanctions on, and monitoring of" countries that might assist North Korea "will be mostly futile".