North Korea appears to be preparing for another nuclear test, but it would be "out of character" if such a test is carried out now, given its leader Kim Jong-un's call for the mass production of a nuclear arsenal, an expert at 38 North said Monday.

Jenny Town, director at the Stimson Center's 38 North, a United States website monitoring North Korea, also said there have been no "notable" movements indicating an imminent nuclear test at the Punggye-ri nuclear test site.

"I would note that Kim Jong-un has recently talked about going into mass production of nuclear warheads. And so I think it would be very out of character for a test to be done now when they're already talking about mass production," she told a press briefing in Seoul.

At a key party meeting held last year, the North's leader ordered an "exponential" increase in its nuclear arsenal and the mass production of tactical nuclear weapons.

The secretive regime has recently released photos of what appears to be tactical nuclear warheads, spawning speculation that Pyongyang may soon conduct what would be the seventh nuclear test.

38 North said North Korea has "created the option" to carry out another nuclear test, such as opening a new entrance into the test tunnel area at the Punggye-ri site.

"(But) we have not seen any indications that they're trying to, for instance, seal off the tunnel, if they're going to do a test they would need to seal the tunnel first," Town said, adding the North could do it without being detected.

Touching on "growing activity" at the North's new experimental light water reactor in the Yongbyon nuclear complex, she said it could be more signs of testing cooling systems or pipelines in advance of putting the reactor into operation.

Meanwhile, 38 North's analysis of nighttime satellite imagery showed North Korea still remains in the dark, but Pyongyang and some industrial sites have emitted more light than in the past.

Imagery showed nighttime light was brighter in the Sadong and Hwasong districts in the capital, as the North's leader ordered the construction of 50,000 new homes.

"If we look closer, we can start to see some small changes that appear to be a result of some of Kim Jong-un's economic priorities and projects that have been going on in the country in the last five years," Martyn Williams, senior fellow at 38 North, told reporters.

As the North still suffers chronic power shortages, only a "huge investment in electric power generation" would help resolve the problem, he added.

Source: Yonhap News Agency