North Korean leader Kim Jong-un declared a resolute nuclear response to threats by the United States during an on-site inspection of the country's test-firing of a Hwasong-17 intercontinental ballistic missile (ICBM) earlier this week, Pyongyang's state media said Saturday.

The missile, launched from Pyongyang International Airport, flew 999.2 kilometers for 4,135 seconds at an apogee of 6,040.9km and landed in the international waters of the East Sea, according to the Korean Central News Agency (KCNA).

"The test-fire clearly proved the reliability of the new major strategic weapon system to be representative of the DPRK's strategic forces and its powerful combat performance as the strongest strategic weapon in the world," it said in an English-language report. The DPRK is the acronym for the North's official name, the Democratic People's Republic of Korea.

It stressed that the firing was carried out under the "intolerable condition" that the "reckless military confrontational moves of the U.S. and other hostile forces" driving regional security to the "red line" have gone beyond the limit. It was referring to large-scale combined military drills recently staged by South Korea with some of key U.S. strategic assets mobilized.

Kim observed the test in person, along with senior North Korean officials, as well as "his beloved daughter and wife," it reported.

The KCNA released several photos that showed his daughter in a white winter jacket and black pants standing and walking together with Kim in front of the missile that sat on a launch truck. The daughter was also seen along with her mother, Ri Sol-ju, watching her father as he instructed military officials.

It marked her first official appearance in state media.

North Korea has never confirmed the existence of Kim's children. South Korean intelligence speculated Kim and his wife got married in 2009 and have two daughters and one son, born in 2010, 2013 and 2017, respectively.

Kim was quoted as saying that the launch of the ICBM has reaffirmed his regime's acquisition of a powerful and reliable capability to counter any nuclear threats.

He "solemnly declared" that "if the enemies continue to pose threats to the DPRK, frequently introducing nuclear strike means, our Party and government will resolutely react to nukes with nuclear weapons and to total confrontation with all-out confrontation."

The report also officially mentioned the existence of Pyongyang's military units in charge of operations of ICBMs for the first time.

Kim urged, "ICBM units and all the units for the operation of tactical nukes" to intensify their training so they can "perfectly discharge their important strategic duty in any situation and at any moment," according to the report.

"This is the first time that North Korea publicly mentioned ICBM units though it was already known there were several such units under its strategic forces," said Shin Jong-woo, a senior analyst at the Korea Defense Security Forum in Seoul.

"It seems like North Korea showed off its advanced ICBM capabilities to the United States with a successful firing of the Hwasong-17 at a high angle," he said.

Experts believe the North has four ICBM units -- three near its border with China and one in the central region.

South Korea's military said Friday the North launched an ICBM, apparently at a lofted angle, which traveled around 1,000 kilometers at an apogee of some 6,100km at a top speed of Mach 22.

On Nov. 3, the North test-fired the same ICBM, which apparently ended in failure.

The Hwasong-17, dubbed "monster" for its size, is known to be capable of carrying multiple warheads with a range of around 15,000km, enough to reach the entire U.S. mainland. (Yonhap)