North Korean leader Kim Jong-un has warned his country is nearing its goal of "equilibrium" in military force with the United States, as the United Nations Security Council strongly condemned the North's latest and "highly provocative" ballistic missile launch over Japan.

Key points: Kim Jong-un expresses great satisfaction over the launch, KCNA reports

Kim Jong-un expresses great satisfaction over the launch, KCNA reports He says the North has nearly completed the building of its nuclear weapons force

He says the North has nearly completed the building of its nuclear weapons force Missile passed over the Japanese island of Hokkaido before landing in the northern Pacific Ocean

The North's official Korean Central News Agency (KCNA) carried his comments a day after US and South Korean militaries detected the missile launch from the North Korean capital of Pyongyang.

The KCNA said the leader expressed great satisfaction over the launch, which he said verified the "combat efficiency and reliability" of the missile and the success of efforts to increase its power.

While the English version of the report was less straightforward, the Korean version quoted him as declaring the missile as operationally ready.

He vowed to complete his nuclear weapons program in the face of strengthening international sanctions, the agency said.

He said the country, despite "limitless" international sanctions, had nearly completed the building of its nuclear weapons force and called for "all-state efforts" to reach the goal and obtain a "capacity for nuclear counter attack the US cannot cope with".

"As recognised by the whole world, we have made all these achievements despite the UN sanctions that have lasted for decades," the agency quoted him as saying.

He said the country's final goal "is to establish the equilibrium of real force with the US and make the US rulers dare not talk about military option for the DPRK".

He indicated more missile tests would be forthcoming, saying all future drills should be "meaningful and practical ones for increasing the combat power of the nuclear force" to establish an order in the deployment of nuclear warheads for "actual war".

The North has promised to "redouble its efforts to increase its strength to safeguard the country's sovereignty and right to existence". ( Reuters: KCNA )

The missile on Friday travelled 3,700 kilometres as it passed over the Japanese island of Hokkaido before landing in the northern Pacific Ocean. It was the country's longest-ever test flight of a ballistic missile.

The North has confirmed the missile as an intermediate range Hwasong-12 — the same model launched over Japan on August 29.

Sorry, this video has expired File footage of previous North Korea missile launches

Missile tests cause of 'grave concerns': UN

Photos published by North Korea's state media showed the missile being fired from a truck-mounted launcher and a smiling Kim Jong-un clapping and raising his fist while celebrating from an observation point.

Kim Jong-un was seen celebrating after the successful launch of the missile. ( Reuters: KCNA )

It was the first time North Korea showed the missile being launched directly from a vehicle, which experts said indicated confidence about the mobility and reliability of the system.

In previous tests, North Korea used trucks to transport and erect the Hwasong-12s, but moved the missiles on separate firing tables before launching them.

Under Mr Kim's watch, North Korea has maintained a torrid pace in weapons tests, including its most powerful nuclear test to date on September 3 and two July flight tests of intercontinental ballistic missiles that could strike deep into the US mainland when perfected.

The increasingly frequent and aggressive tests have added to outside fears the North is closer than ever to building a military arsenal that could viably target the US and its allies in Asia.

The tests, which could potentially make launches over Japan an accepted norm, are also seen as North Korea's attempt to win greater military freedom in the region and raise doubts in Seoul and Tokyo that Washington would risk the annihilation of a US city to protect them.

It was the first time North Korea showed the missile being launched directly from a vehicle. ( Reuters: KCNA )

Prior to the launches over Japan, North Korea had threatened to fire a salvo of Hwasong-12s toward Guam, the US Pacific island territory and military hub the North has called an "advanced base of invasion."

The UN Security Council accused North Korea of undermining regional peace and security by launching its latest missile over Japan and said its nuclear and missile tests "have caused grave security concerns around the world" and threaten all 193 UN member states.

The Security Council stressed in a statement after a closed-door emergency meeting that all countries must "fully, comprehensively and immediately" implement all UN sanctions.

A man watches a television broadcasting a news report on North Korea firing a missile that flew over Japan. ( Reuters: Kim Hon-ji )

AP