North Korea on Monday fired a fresh warning that it would take nuclear "measures" if the United States does not end what the communist state described as provocations.

North Korea's ambassador to the United Nations, Ri Tong-Li, said that Pyongyang was "ready" with measures that would "demonstrate the power of the self-defensive nuclear deterrent."

Asked at a news conference for more detail, Ri said: "We are keeping ourselves restrained from taking the additional measures, but it is totally dependent on the attitude of the US.

"What kind of additional measures, I think you can wait and see later," he said.

North Korea earlier this month also threatened to react against US "blackmail," although think tanks that assess satellite imagery said there was no sign of an imminent nuclear or long-range missile test.

North Korea, however, has carried out a series of short-range missile tests. Ri described the maneuvers as "routine" and said that it was instead the United States which was "hellbent on provocations" through joint exercises with ally South Korea.

Ri also accused the United States of "human rights conspiracies" after a UN commission last month said that North Korea was carrying out executions, forced labor and other abuses so pervasive that they draw parallels to Nazi Germany's crimes against humanity.

Ri said that the United States was "clinging on the issue of human rights" after efforts to stop North Korea's nuclear program failed. Ri accused South Korea's non-governmental organizations of "brainwashing" North Koreans, who often report abuses after defecting.

"NGOs of South Korea (are) crazy about dollars of US," Ri said. "They were hellbent on whatever means -- luring, abducting Korean citizens."

Ri said that groups that work with North Koreans who enter China were "camouflaging their real colors" by portraying themselves are missionaries.

The UN Commission of Inquiry said that North Korea did not cooperate and that it based its findings on research that included 240 confidential interviews and public testimony from 80 witnesses.