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 (622 miles) 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 "a series of stronger military offensive" would be launched until Washington and Seoul 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.

Confirmation of the launch -- which South Korea's military had reported Wednesday -- came with relations between the two Koreas at a low point.

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 nuclear weapons against the allies.

Seoul described Wednesday's launch as "a grave provocation that damages the peace and security of the Korean peninsula".

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

Foreign ministers of the G7 bloc of major democracies plus the European Union said Thursday they "condemn in the strongest terms North Korea's brazen launch of another ICBM," and reiterated their demand that Pyongyang abandon its nuclear weapons and ballistic missile programs in an "irreversible" manner.

"North Korea continues to expand its unlawful nuclear and ballistic missile capabilities and to escalate its destabilizing activities," G7 ministers said. "These launches pose a grave threat to regional and international peace and stability, and undermine the global non-proliferation regime."

- 'Provocative' US actions -

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 North Korea would take "decisive action" if its maritime military demarcation line was crossed.

Washington said in April 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.

"I expect the North to continue firing missiles similar to Hwasong-18 through the end of August while the joint South Korea-US military exercises are scheduled," Choi Gi-il, a professor of military studies at Sangji University, told AFP.