Seoul: North Korea staged an apparent nuclear test of six to seven kilotons on Tuesday in a striking act of defiance that, if confirmed, is sure to trigger global condemnation from enemies and allies alike. (Agencies)
Seismic readings from the area around North Korea's nuclear test site detected a "suspected explosion", according to China's Earthquake Administration, and South Korea said all the signs pointed to a test.
"We suspect North Korea has pushed through with a third nuclear test," South Korean defence ministry spokesman Kim Min-Seok told reporters, putting the yield at significantly more than North Korea's two previous tests in 2006 and 2009.
North Korea had provided China and the United States with advance warning that a test was imminent, Kim said, after the communist state called for "high-intensity" action and further long-range rocket launches.
In Vienna, the Comprehensive Nuclear Test Ban Treaty Organisation said the location of Tuesday's explosion was "roughly congruent" with the 2006 and 2009 tests, and labeled the event a "clear threat" to international peace.
The two previous tests triggered waves of UN sanctions, and the Security Council was set to meet in emergency session on Tuesday morning in New York in response to the apparent third detonation.
The response of China, North Korea's economic and diplomatic patron, will be key. While restraining US-led allies from stronger action against Pyongyang in the past, Beijing had pressed the country to hold off on the third test.
The apparent test came despite a "strong warning" from China to the North, a Security Council diplomat said.
For nuclear experts, the key question will be whether North Korea used up more of its scarce reserves of plutonium for the suspected third test, or used uranium in a new and self-sustaining path to atomic detonations.
Seoul: North Korea staged an apparent nuclear test of six to seven kilotons on Tuesday in a striking act of defiance that, if confirmed, is sure to trigger global condemnation from enemies and allies alike.