North Korea on Wednesday aired a video image of the submarine-launched ballistic missile (SLBM) in flight after its launch in April.

A documentary aired earlier in the day by the country's state-run Korean Central TV Station showed an SLBM being launched from a submerged submarine and soaring vertically into the air.

Kim Jong-un watched the launch from the shore and the flight scene was replayed several times with the film roughly titled "(he) displays the zenith of a revolution."

The video also carried an image of Kim and North Korean officials including Ri Man-gon, director handling munitions for the ruling Workers' Party of Korea, applauding and cheering after the missile shot up into the sky.

In the early morning of April 23, North Korea fired off the SLBM from a 2,000-ton Sinpo-class submarine and claimed in news reports the next day that it has made another successful ballistic missile launch. This launch in particular was meaningful because it was made from under the sea.

After tracking the missile's flight path, South Korea's military officials said the launch failed because it flew just 30 kilometers, far short of an SLBM's predicted minimum range of some 300 km. Officials later said the launched missile split into about three pieces after exploding in the air.

Following the release of the video, South Korean officials and experts started to speculate on the possible intention of its publication which is timed to coincide with high-ranking North Korean official Ri Su-yong's rare visit to China this week.

Media reports out of Beijing said North Korean leader Kim Jong-un and Chinese President Xi Jinping expressed their wish to improve ties that had been strained by the North's nuclear weapons program.

"This kind of video released while vice chairman (of the North Korean ruling party's central committee) Ri Su-yong is visiting China seems pretty intentional," Kim Yong-hyun, a professor of North Korean studies at Dongguk University, said.

"It seems that the North is asserting its dual-policy of simultaneously seeking nuclear and economic development ahead of any substantial talks with China on the nuclear issue." (Yonhap)