The KCNA news agency said North Korean leader Kim Jong Un had called for an improvement in the country's nuclear attack capability. He ordered more tests after watching the launch of two short-range missiles on Thursday.
"Dear comrade Kim Jong Un said work ... must be strengthened to improve nuclear attack capability," Pyongyan's state news agency KCNA said on Friday.
It added that Kim had issued instructions for "combat tasks to continue ... tests to assess the power of newly developed nuclear warheads and tests to improve nuclear attack capability."
Just a day earlier, the North launched twoshort-range ballistic missiles
from the eastern part of the country which fell into the East Sea (Sea of Japan) shortly afterwards.
KCNA said Thursday's launch was part of a nuclear strike exercise, whose aim was to simulate conditions for "exploding nuclear warheads from the preset altitude above targets in the ports under enemy control."
Kim threatens Seoul
Watching the exercise, Kim reiterated an earlier threat to launch an immediate nuclear attack if annual joint military drills, which the "saber-rattling" South Korea and US started on Monday, should harm "even a single tree or a blade of grass" on North Korean territory, state media said.
Since the military exercises began, expanded this year in response to the North's nuclear test, Pyongyang has issued daily warnings and statements, talking up its nuclear strike capabilities and threatening to turn Seoul and Washington into "flames and ashes."
South Korea's Unification Ministry spokesman Jeong Joon-hee swiped at Kim's comments, describing them as "simply rash and thoughtless behavior by someone who has no idea how the world works."
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, prompting the United Nations Security Council to impose further sanctions on Pyongyang.
Conducting more nuclear tests would violate past UN resolutions, which also ban ballistic missile tests.
According to analysts, Pyongyang has a large stockpile of short-range missiles and is developing long-range and intercontinental ballistic missiles (ICBMs).
Kim was quoted by state media earlier in the week as saying his country already had miniaturized nuclear warheads to mount on ballistic missiles. But South Korea said it did not believe the North had, yet, successfullyminiaturized the technology
On Thursday, UN Secretary-General Ban Ki-moon urged Pyongyang to avoid any further "destabilizing acts," echoing similar comments from regional leaders.
mm/msh (AFP, Reuters)