Nuclear-armed North Korea has said its launch of a ballistic missile over Japan on Tuesday was a prelude to more military operations directed at the American territory of Guam, which it called "an advanced base of invasion", according to state-run media.
The country's Korean Central News Agency reported that leader Kim Jong-un presided over the launch of the "ultra-modern rocket system", the first missile ever fired from the capital Pyongyang.
The intermediate-range missile, identified by the North Koreans as the Hwasong-12, crossed Japan's northern Hokkaido Island in a major escalation that triggered global alarm and a furious response from the government in Tokyo.
The news agency quoted Kim as saying that "like a real war", the latest drill was "the first step of the military operation of the KPA (Korean People's Army) in the Pacific and a meaningful prelude to containing Guam".
A visibly unsettled Japanese Prime Minister Shinzo Abe said it was an ''unprecedented, serious and grave threat'', while the UN Security Council called an emergency meeting at Tokyo and Washington's request.
The Guam governor's office said in a statement there is no change in the island's threat level.
"We knew, based on North Korea events in previous years, that with the joint exercise between the US, South Korea, and its Allies, we can expect rhetoric and activity in North Korea," said George Charfauros, Guam's homeland security adviser.
KCNA said the launch was in direct response to the joint US-South Korean military drills, as well as to mark the anniversary of the Japan-Korea treaty of 1910, which saw Japan annex the Korean peninsula.
Kim has also ordered more rocket drills targeting the region, the state media said.
South Korean presidential spokesman Park Su-hyun said in a statement that the country's President Moon Jae-in and Japanese prime minister Shinzo Abe both now believe "pressure on North Korea should be raised to its limit so that North Korea will voluntarily come to the table for dialogue".
The UN Security Council called the missile launch "outrageous", demanding North Korea cease all missile testing.
While the statement said the regime's actions were a threat to all UN member states, it did not threaten new sanctions against Pyongyang.
Russia and China said US military activity in the region was partly to blame for the increase in tensions, and urged negotiations, a BBC report said.
Arriving for a visit to Japan, British Prime Minister Theresa May called on China to put more pressure on North Korea, saying that Beijing had a key role in the international response to Pyongyang's "reckless provocation".
The launch also drew a strong rebuke from US president Donald Trump who again warned that "all options are on the table" to act against North Korea.
It was the fourth missile North Korea fired in four days - Pyongyang tested three short-range ballistic missiles, one of which failed, from Kangwon province that landed in water off the Korean Peninsula.
Earlier in August, Pyongyang first threatened to fire missiles towards Guam where some 160,000 US citizens live.
The last time a North Korean rocket overflew Japan was in 2009, when Pyongyang said it was a satellite launch. Washington, Seoul and Tokyo believed it was a clandestine test of an intercontinental ballistic missile (ICBM).
Pyongyang last month carried out two overt ICBM tests that appeared to bring much of the US mainland within reach for the first time and heightened strains in the region.