SEOUL • North Korean leader Kim Jong Un watched a ballistic missile launch test and ordered the country to improve its nuclear attack capability by conducting more tests, according to the official KCNA news agency.

The report did not say when the test took place, but it was likely referring to North Korea's launch of two short-range missiles on Thursday that flew 500km and splashed into the sea.

"Dear comrade, Mr Kim Jong Un said work ... must be strengthened to improve nuclear attack capability, and issued combat tasks to continue nuclear explosion tests to assess the power of newly developed nuclear warheads and tests to improve nuclear attack capability," KCNA said yesterday.

The North Korean leader was quoted in state media earlier in the week as saying his country had miniaturised nuclear warheads to mount on ballistic missiles.

Tensions have risen sharply on the Korean peninsula after the North conducted its fourth nuclear test in January and fired a long- range rocket last month, leading to the United Nations Security Council adopting a new sanctions resolution.

Russia and China, allies of North Korea, yesterday told the pariah state it should resume international talks over its nuclear weapons programme and heed a Security Council resolution that bans ballistic missile tests. Russian Foreign Minister Sergei Lavrov and Chinese Foreign Minister Wang Yi made the joint call after holding talks in Moscow. Neither country recognised Pyongyang's nuclear ambitions, they said.

North Korea has a large stockpile of short-range missiles and is developing long-range and intercontinental ballistic missiles (ICBMs).

When asked about Mr Kim's comments, South Korea's Unification Ministry spokesman Jeong Joon Hee said: "It's rash and thoughtless behaviour by someone who has no idea how the world works."

UN Secretary-General Ban Ki Moon called on Pyongyang to "cease destabilising acts", adding that he remained "gravely concerned" by the situation.

South Korea said it did not believe the North had successfully miniaturised a nuclear warhead or deployed a functioning ICBM.

The United States Defence Department said this week it had seen no evidence that North Korea had succeeded in miniaturising a warhead.

However, Admiral Bill Gortney, the officer responsible for defending US air space, told a US Senate panel on Thursday it was "prudent" for him to assume North Korea could both miniaturise a warhead and put it on an ICBM that could target the US.

"Intel community gives it a very low probability of success, but I do not believe the American people want (me) to base my readiness assessment on a low probability," he said.

North Korea has issued nearly daily reports in recent days of Mr Kim's instructions to fight South Korea and the US as the two allies began large-scale military drills.

North Korea called the annual drills "nuclear war moves" and threatened to respond with an all-out offensive. Mr Kim last week ordered his country to be ready to use nuclear weapons in the face of what he sees as growing threats from enemies.

The US and South Korea remain technically at war with North Korea because the 1950-1953 Korean War ended in a truce, instead of a peace agreement.

REUTERS