North Korea's foreign minister warned Tuesday Pyongyang had the power to conduct a "pre-emptive strike" on the United States, following joint US-South Korea military drills earlier this week.

Ri Su-yong also slammed a UN rights inquiry released last year that laid bare Pyongyang's brutality as a "misdeed" and called for a resolution on North Korea's rights record to be "revoked immediately."

Speaking at the United Nations in Geneva, Ri said the joint military exercises that kicked off Monday were "unprecedentedly provocative in nature" and could spark a war.

"The DPRK (Democratic People's Republic of Korea) cannot but bolster its nuclear deterrent capability to cope with the ever-increasing nuclear threat of the US," he told the UN Disarmament Conference.

"Now the DPRK has the power of deterring the US and conducting a pre-emptive strike as well if necessary."

The annual joint exercises always trigger a surge in warlike rhetoric on the divided peninsula.

North Korea fired two short-range Scud missiles into the sea off its east coast on Monday, and South Korea's Yonhap news agency reported Tuesday that Pyongyang may be readying to test fire a medium-range missile.

Missile tests have long been a preferred North Korean method of expressing displeasure with what it views as confrontational behaviour by the South and its allies, though Seoul and Washington insist the exercises are defence-based in nature.

- 'Overwhelming sorrowful pity' -

Later Tuesday, Ri spoke to the UN Human Rights Council, angrily denying there were any "widespread" violations in a country whose political system "enjoys the eternal vitality."

A UN report released last year concluded that North Korea was committing rights violations "without parallel in the contemporary world".

Based on the testimony of North Korean exiles, it detailed a vast network of prison camps and documented cases of torture, rape, murder and enslavement.

The report formed the basis of a resolution adopted by the UN General Assembly in December that urged the Security Council to consider referring Pyongyang to the International Criminal Court -- putting it under unprecedented pressure.

But in January, defector Shin Dong-Hyuk -- one of those who testified for the inquiry -- acknowledged that some elements of his story as told in a book were inaccurate, although he stressed that the crucial details of suffering and torture still stood.

North Korea has since leapt on this as proof that the entire report is invalid, and Ri reiterated this on Tuesday.

"In any court, a ruling based on false testimony is to be nullified," he said.

"The anti-DPRK resolutions based on the... report should be revoked immediately without delay."

He pointed out that the fact that his country's current political system had survived despite "years of hardships" proved there were no widespread rights violations.

The country suffered devastating famine in the 1990s, and remains hugely impoverished with malnutrition widespread.

"Those hostile towards us cannot understand the ties of blood between the leader and the popular masses and the world of single-minded unity that can be found only in the DPRK," he said.

His comments were almost immediately shot down by South Korea's vice foreign minister, who said he felt "an overwhelming sorrowful pity" upon hearing them.

"The minister knows better than anyone else about the horrific human rights situation in the DPRK and the grave concern verging on despair of the international community over the situation," Cho Tae-yul said.