North Korea successfully conducted a submarine-launched ballistic missile test in late December, about a month after a previous test failed, a U.S. news report said Tuesday.

The ejection test of a KN-11 missile from a submerged submarine took place on Dec. 21 near the eastern port of Sinpo, the Washington Free Beacon reported, citing unidentified U.S. defense officials.

The test followed a Nov. 28 test in which a KN-11 missile failed to leave the water. The failure damaged the North's first missile submarine, which officials identified as the Gorae, which means whale in Korean, the report said.

The report provided no further details, including if the missile's engine ignited after the ejection or whether the missile took flight.

But it quoted an unidentified official as saying that based on the latest successful ejection test, North Korea could be as little as a year away from deploying a submarine armed with a nuclear-tipped missile.

Cmdr. Bill Urban, a spokesman of the U.S. Defense Department, declined comment, citing intelligence matters.

Later in the day, the North Korea-monitoring website, 38 North, said that the report of last month's SLBM test appears to be true and supported by new commercial satellite imagery of the Sinpo South Shipyard. Despite November's failed test, the North is continuing to actively pursue its SLBM development program, it said.

Satellite imagery shows activity at the secure submarine area of the shipyard that is similar to the level of activity that has been previously seen prior to an SLBM test in May, 38 North said.

In addition, 38 North said that the structure used to support a rocket engine, missile or launch tube, which is usually present either immediately prior to or shortly after a test is conducted, is in place, and the SINPO-class submarine docked at the secure boat basin was seen with netting concealing ongoing work,

"North Korea's development of a SLBM and associated ballistic missile submarine has the potential to present a significant threat in the future. However, the development of an operational system will be an expensive, time-consuming endeavor with no guarantee of success," 38 North said.

In May, North Korea claimed it successfully carried out an SLBM test underwater, renewing tensions on the Korean Peninsula amid concerns that the North's SLBM capability, if fully developed, would pose a serious threat because its mobile nature would make it very difficult to detect preparations for a launch.

But experts said it was believed not to be a full-scale test, but an "ejection" test conducted in an early stage of developing SLBM capabilities. U.S. officials said the North also exaggerated progress and is many years away from developing an SLBM.

Under U.N. resolutions, the North is banned from any ballistic missile activity. (Yonhap)