North Korea's latest missile launch is its third in three weeks and its 12th this year, underscoring Kim Jong Un's determination to advance his regime's technical capabilities and his continued defiance of the international community.
The regime launched a new short-range ballistic missile, similar to a Scud, yesterday and it flew about 450km to land inside Japan's exclusive economic zone.
"The firing of the ballistic missile of this time is extremely problematic in terms of safety of aircraft and ships," Yoshihide Suga, Japan's chief cabinet secretary, told reporters in an emergency news conference. "It also clearly violates resolutions adopted by the United Nations Security Council."
Prime Minister Shinzo Abe, returning from a G-7 meeting in Italy, said that Japan will work with the United States to deter North Korea.
Kim has been pushing ahead with his weapons programme at a rate that has alarmed analysts and policymakers, ordering the launches of a variety of rockets that appear part of his ambition to obtain an intercontinental ballistic missile capable of reaching the mainland United States.
He has overseen the launch of 78 missiles since he took power 5 1/2 years ago, compared to the 16 missiles fired during the 17 years that his father, Kim Jong Il, was at the helm.
Although the missiles sometimes explode shortly after launch, the North Koreans have had a surprisingly good success rate, said Shea Cotton, an expert at the James Martin Centre for Nonproliferation in California.
Of the 78 missiles launched under Kim Jong Un, 61 have succeeded, giving him a 78 per cent success rate, Cotton said.
The latest missile was launched from an airfield near Wonsan, on North Korea's east coast, according to the US Pacific Command and South Korea's joint chiefs of staff.
"The missile was tracked for six minutes until it landed in the Sea of Japan," Pacific Command said.
Moon Jae In, South Korea's new President, ordered an emergency national security council meeting to discuss the latest launch, and his joint chiefs said the South Korean military was "maintaining full preparedness".
Before the latest launch, US Defence Secretary Jim Mattis said that war with North Korea would "probably the worst kind of fighting in most people's lifetimes".
North Korea was threatening the United States with its nuclear weapons, but its conventional weapons could cause huge devastation in South Korea, where half the population lives in the Seoul area, within firing range of North Korean artillery.
"The bottom line is it would be a catastrophic war if this turns into a combat if we're not able to resolve this situation through diplomatic means," Mattis told CBS News.