'Close to a nuclear test'

A US research institute said Tuesday that while satellite pictures showed heightened activity around the Korean peninsula, it was not enough to indicate an underground atomic explosion was imminent.

Following the report, US State department spokesperson Jen Psaki told reporters in Washington was closely watching events in the area and urged Pyongyang not to do anything that would threaten peace in the region.

"We have certainly seen the press reports…regarding possible increased activity in North Korea's nuclear site," Psaki said.

"We continue to urge North Korea to refrain from actions that threaten regional peace and security and to comply with its international obligations."

Meanwhile, South Korea warned Tuesday that its "military is currently detecting a lot of activity in and around the Punggye-ri nuclear test site," defense ministry spokesperson Kim Min-Seok told a press briefing. Kim added the North's nuclear weapons program was at a stage where it could conduct a "test at any moment."

The warning comes as US President Barack Obama departed on a week-long tour of Asia. Obama is due to visit Japan and South Korea where he will discuss a means to deal with North Korea's nuclear weapons program.

North Korea has conducted three nuclear tests, in 2006, 2009, and 2013 – all at the Punggye-ri test site located in the northeast of the country.

Last month, North Korea warned it would not rule out "a new form" of nuclear test following the United Nations Security Council's condemnation of Pyongyang for releasing ballistic missiles.

jlw/kms (AP, Reuters)