North Korea Says Conducted New Test Of Solid-fuel ICBM

North Korean leader Kim Jong Un personally oversaw the successful test of the country's newest intercontinental ballistic missile, state media reported Thursday, days after Pyongyang threatened to down any US spy planes that enter its airspace.

A beaming Kim, flanked by his wife and key aides, was shown in state media images applauding enthusiastically after the launch of the solid-fuel Hwasong-18 on Wednesday.

The ICBM, which North Korea has fired only once before, in April, flew 1,001 kilometres at a maximum altitude of 6,648 km before splashing into the East Sea, also known as the Sea of Japan, the official Korean Central News Agency reported.

The launch was a "grand explosion" that shook "the whole planet", KCNA said. State media footage showed the missile blasting off into the sky.

Kim vowed that "a series of stronger military offensive" would be launched until the United States and South Korea change their policies towards North Korea, the agency added.

Citing the "unstable situation" on the Korean peninsula, Kim also called for "more intense efforts" to boost North Korea's nuclear arsenal.

The confirmation of the launch -- which the South Korean military had reported on Wednesday -- came with relations between the two Koreas at one of their lowest points ever.

Diplomacy is stalled and Kim has called for ramping up weapons development, including tactical nukes.

In response, Seoul and Washington have boosted security cooperation, vowing that Pyongyang would face a nuclear response and the "end" of its current government were it to ever use its nuclear weapons against the allies.

Seoul described Wednesday's launch as "a grave provocation that damages the peace and security of the Korean peninsula". The United Nations, the United States and its allies also strongly condemned it.

Japan's top government spokesman Hirokazu Matsuno told reporters that the test appeared to be of the same solid-fuel ICBM missile first fired in April -- warning such missiles "have an advantage in immediate launch" over Pyongyang's liquid fueled missiles.

Wednesday's test was conducted from a launchpad made to look like a natural park surrounded by ponds and trees at a Kim family private mansion on the east side of Pyongyang, Seoul-based specialist site NK News reported.

It came after North Korea on Monday accused a US spy plane of violating its airspace and condemned Washington's plans to deploy a nuclear missile submarine near the Korean peninsula.

The US has "intensified espionage activities beyond the wartime level" with "provocative" spy plane flights, Pyongyang said.

"There is no guarantee that such shocking accident as downing of the US Air Force strategic reconnaissance plane will not happen in the East Sea of Korea," a North Korean defence spokesperson said.

Kim's powerful sister Kim Yo Jong also slammed the purported US spy aircraft airspace violations, and warned that North Korea would take "decisive action" if its maritime military demarcation line was crossed.

The United States said in April that one of its nuclear-armed ballistic submarines would visit a South Korean port for the first time in decades, without specifying an exact date.

South Korea and the United States are set to start their major annual joint military exercises, known as Ulchi Freedom Shield, next month.

North Korea regards all such exercises as rehearsals for invasion and has described them as "frantic" drills "simulating an all-out war against" Pyongyang.

Although conducting ICBM launches is expensive, particularly given the dire economic conditions in North Korea with reports of food shortages and starvation, Choi said Pyongyang had "got enough missiles ready" to continue its testing blitz.

Recent satellite images suggest Pyongyang is preparing for a massive military parade later this month to mark the July 27 Korean War armistice anniversary, known as Victory Day in the North.