The missile was fired at 6:30 p.m. Saturday (5:30 a.m. ET), South Korean officials said, and appears to have flown about 30 km (about 19 miles) -- well short of the 300 km (roughly 186 miles) that would be considered a successful test.
North Korean state news agency KCNA claimed the launch was successful, and said North Korean leader Kim Jong Un "guided on the spot the underwater test-fire of strategic submarine ballistic missile."
"At the observation post he was briefed on the plan for the test-fire and gave an order for it," KCNA reported. "As soon as the order was issued, the submarine submerged as low as the biggest depth of waters for launching and fired the ballistic missile. The test-fire was aimed to confirm the stability of the underwater ballistic launching system in the maximum depth of waters."
One U.S. official said Saturday the launch "was provocative but not a threat to the U.S. and the missile was fired away from South Korea and Japan." But another U.S. official noted that after previous launch attempts by Pyongyang that didn't appear to be successful, this one seems to have gone much better.
"North Korea's sub launch capability has gone from a joke to something very serious," this official said. "The U.S. is watching this very closely."
U.S. denounces launch
Launching a missile from a submarine has always been a military priority for North Korea, CNN's Barbara Starr reports, and if this test was successful, it would be a military victory for Pyongyang.
But such a launch is in violation of U.N. Security Council resolutions, the U.S. State Department said.
"We have seen the reports that North Korea launched what appeared to be a ballistic missile from a submarine in the Sea of Japan," State Department spokesman John Kirby said in a statement. "Launches using ballistic missile technology are a clear violation of multiple U.N. Security Council resolutions."
"We call on North Korea to refrain from actions that further destabilize the region and focus instead on taking concrete steps toward fulfilling its commitments and international obligations.
"The United States remains steadfast in its commitments to the defense of its allies. We will continue to coordinate closely with the ROK, Japan, and other allies and partners," Kirby added.
Previous launch a failure
Saturday's launch comes about a week after another attempt, which was apparently unsuccessful.
A U.S. defense official said April 14 that U.S. Strategic Command systems detected and tracked an attempted North Korean missile launch, but there was "no evidence the missile reached flight," a U.S. official told Starr.
Tensions have risen on the divided Korean peninsula this year as Pyongyang has made a series of assertions about developments in its military capability.
South Korea's military did not specify what sort of missile was part of the April 14 test, but South Korean media reported it involved an intermediate-range Musudan missile.
Pyongyang carried out its fourth nuclear test in January. It said it succeeded in miniaturizing nuclear warheads to fit on medium-range ballistic missiles, which U.S. intelligence analysts say is probably true.
South Korean military on high alert
Ballistic missiles are missiles fired in an arc toward their targets.
CNN's Paula Hancocks said it was not yet known whether the latest North Korean test was a success. But she said the ability to launch ballistic missiles from submarines makes possible launch points far more difficult to detect.
The South Korean military was on high alert following the test, Hancocks said. (CNN)
