North Korea may already be preparing to carry out its threat of a fourth nuclear test, in response to a United Nations resolution which called for Kim Jong-un to be referred to the International Criminal Court for human rights abuses.

On Thursday, Pyongyang's foreign ministry called) the resolution's approval a "grave political provocation" orchestrated by the US. An unidentified military spokesman also said that the North's war deterrence would be strengthened in an "unlimited manner," as a reaction against US hostility, which is "compelling us not to refrain from conducting a new nuclear test any longer."

A leading US think-tank claims to have discovered evidence that North Korea may already be escalating their nuclear program. Using satellite images, the US-Korea Institute at John Hopkins University said it has detected signs that the state may be readying a plutonium production reactor in preparation for restarting it.

Joel Wit, manager of the 38 North website, told VICE News that they had spotted several indicators at the Yonghyon Nuclear Scientific Research Center. "In this particular incidence what they seem to have done is shut down the reactor and are probably transferring some of that material to another facility that produces the finished product." While this facility doesn't deal with nuclear tests, Wit said: "It's all part of building nuclear weapons."

Researchers have also spotted steam rising from a re-processing plant at the Yongbyon Nuclear Scientific Research Center, the think tank said.

Speaking in April, South Korea's Foreign Minister Yun Byung-se warned against the "unyielding nuclear ambitions" of North Korea, and said: "If North Korea goes ahead with another nuclear test as it has publicly warned, it will be a game changer."

Scott Snyder, Korea expert at the Council on Foreign Relations, told VICE News that if the secretive state's threat was acted upon, it would be consistent with their previous behavior, but would also mark the first time a nuclear test was triggered by a UN human rights action.

"There is a pattern of DPRK tests in response to negative developments at the UN, but thus far these have been restricted to UN condemnation of DPRK missile launches."

The country's previous three tests were conducted in 2006, 2009, and 2013.

However, in an apparent continuation of Pyongyang's erratic political behavior, Russian Foreign Minister Sergey Lavrov also announced on Thursday that North Korea is ready to resume the six-party nuclear talks which were halted in 2009.

Lavrov also said that a letter from Kim Jong-un — presented to Russian president Vladimir Putin by Choe Ryong Hae, a North Korean special envoy, who visited Moscow earlier this week — had expressed a desire to "cooperate on settling the problems that still remain on the Korean Peninsula."

Tuesday's UN resolution passed with approval from 119 countries, with 19 opposed and 55 abstaining. An attempt, led by Cuba, to have references to the International Criminal Court dropped from the text were unsuccessful.

Russia and China voted against the resolution, as did Egypt, Myanmar, Zimbabwe, Iran, Sudan, Syria and Sri Lanka.

Speaking before the vote, the DPRK delegation at the UN said that the European Union and Japan had taken sides with the "United States' hostile policy against the DPRK," and thus had "fabricated" the draft resolution. They claimed it was based on "a compilation of groundless political accusations and contradictions (with) no qualification and credibility to be recognized as an official document of the United Nations."

The delegation added: "We have consistently maintained a position of rejecting confrontation and giving priority to dialogue and cooperation in the area of human rights and, from this perspective, clearly stated our renewed intention this time around to engage in board-ranging constructive cooperation…

"We do not feel any necessity to appeal to anyone to come and see the reality of our country where politics and social system are all for the people and guarantee their human rights."

After the vote the DPRK delegation said that the "so-called human rights dialogue advocated by the EU is only intended to pursue sinister political purposes of eliminating the ideology and social system of the DPRK." It added that the government would continue to consolidate and develop their socialist system.

Jeff Rathke, a White House spokesperson, said at Wednesday's daily press briefing: "Denuclearization is the top priority with respect to North Korea. So I'm not familiar with that statement, but it would certainly be unfortunate to threaten with that kind of activity in response to the legitimate focus on North Korea's human rights situation by the international community."

He added that if the country wanted the six-party talks to be reinitiated, they had to prove it through their actions. "We're not interested in talks for talks' sake only. North Korea has to take steps, and those are clear."

The original six-party talks included North and South Korea, the United States, Japan, China, and Russia. They were discontinued after a failed 2009 satellite launch — believed by the international community to be a missile equipment test — was condemned by the United States and the UN Security Council.

At the time North Korea said in a statement that it would "never again" take part in the negotiations and would not be bound by any deal struck at such talks.