The United States is urging North Korea to refrain from a new nuclear test amid indications of "heightened activity" at Pyongyang's Punggye-ri test site.
"We have certainly seen the press reports ... regarding possible increased activity in North Korea's nuclear test site," State Department spokeswoman Jen Psaki said. "We are closely monitoring the situation on the Korean peninsula."
"South Korean news reports quoted the South Korean government as saying on Tuesday that heightened activity had been detected at North Korea's underground nuclear test site, indicating possible preparations for another atomic test.
"The reports come just before U.S. President Barack Obama is due in Japan and South Korea, where he will discuss ways to deal with North Korea's nuclear weapons program. Obama is due in Tokyo on Wednesday and in Seoul on Friday."
On 38North.org, a blog that monitors North Korea, analyst Jack Liu writes:
"In the six-week period from early March 2014 until April 19, imagery shows an increase in activities at the Main Support Area. This area was used to manage operations and handle personnel and equipment during preparations at the West Portal area for the February 2013 nuclear detonation ...
"Recent press speculation has focused on the possibility of a nuclear detonation during US President Barack Obama's upcoming visit to Seoul on April 24-25. That may be possible but appears unlikely based on the limited commercial satellite imagery available and observations of past North Korean nuclear tests."