North Korea on Tuesday threatened to conduct a fresh underground nuclear test and fire long-range missiles in response to U.S. sanctions and pressure.

The threat took the slightly eccentric form of a poem broadcast on state TV. Entitled "This is [North] Korea's reply," the verses read in part, "They'll know the stirring sound of explosions from an underground nuclear test that will be conducted with burning anger and the justice done by the sun people" against the U.S.

"No longer patient, [North] Korea will launch a series of Kwangmyongsong rockets into the boundless universe and conduct a succession of nuclear tests of justice," the unnamed poet warbled on. "They'll know how dreadful [North] Korea's revenge will be."

In October last year, the deputy chief of the North's mission to the UN said the North will conduct a "new type" of nuclear test.

But a South Korean military spokesman said no special movements of N orth Korean forces have been detected.

Meanwhile, a North Korean newspaper the same day warned the country "could undergo a more severe hardship in the future" than the famine of the 1990s.

The official Rodong Sinmun added, "Today, our revolution is moving forward in an unprecedentedly challenging and tense situation."

