US president Donald Trump has warned North Korea that all options are on the table after the reclusive regime fired a ballistic missile over the Japanese island of Hokkaido.
World leaders have condemned the show of force and New Zealand Foreign Affairs Minister Gerry Brownlee said the country stood beside Japan, a strategic economic partner.
The missile test further increased tension in east Asia as US and South Korean forces conduct annual military exercises on the Korean peninsula, angering Pyongyang, which sees the war games as a preparation for invasion.
The United Nations Security Council has scheduled an emergency session.
The launch into the sea early on Tuesday provoked a sharp reaction from Japan's Prime Minister Shinzo Abe, who said the show of force was unprecedented and a grave threat.
The test appeared to have been of a recently developed intermediate-range Hwasong-12 missile, experts said.
The New Zealand government denounced the missile launch and the Ministry of Foreign Affairs and Trade reviewed its travel advisory for Japan.
Mr Brownlee said the missile launch was a dangerous new escalation and a totally unacceptable threat in a region of considerable importance to New Zealand.
New Zealand stood by Japan, Mr Brownlee said, and he called on North Korea to attend talks to de-escalate a volatile situation.
Mr Trump said the world had received North Korea's latest message "loud and clear".
"This regime has signalled its contempt for its neighbours, for all members of the United Nations, and for minimum standards of acceptable international behaviour," Mr Trump said in a statement.
"Threatening and destabilising actions only increase the North Korean regime's isolation in the region and among all nations of the world. All options are on the table," he said.
Earlier this month, North Korea threatened to fire four Hwasong-12 missiles into the sea near the US Pacific territory of Guam.
'Unprecedented, serious and a grave threat'
North Korea has conducted dozens of ballistic missile tests under its young leader, Kim Jong Un, the most recent on Saturday, but firing projectiles over mainland Japan is rare.
"North Korea's reckless action is an unprecedented, serious and a grave threat to our nation," Japanese Prime Minister Shinzo Abe told reporters on Tuesday.
Mr Abe said he spoke to Mr Trump on Tuesday and they agreed to increase pressure on North Korea. Mr Trump also said the United States was "100 percent with Japan", Mr Abe told reporters.
Earlier this month, the 15-member Security Council unanimously imposed new sanctions on North Korea in response to two long-range missile launches in July.
South Korea's military said the missile was launched from near the North Korean capital, Pyongyang, and flew 2700 km, reaching an altitude of about 550 km.
"We will respond strongly based on our steadfast alliance with the United States if North Korea continues nuclear and missile provocations," the South's foreign ministry said in a statement.
Four South Korean fighter jets bombed a military firing range on Tuesday after President Moon Jae-in asked the military to demonstrate capabilities to counter North Korea.
North Korea remained defiant.
"The US should know that it can neither browbeat the DPRK with any economic sanctions and military threats and blackmails nor make the DPRK flinch from the road chosen by itself," North Korea's official Rodong Sinmun said later on Tuesday, using the initials of the North's official name, the Democratic People's Republic of Korea.
In Japan, television and radio broadcasters broke into their regular programming with a "J-Alert" warning citizens of the missile launch. Bullet train services were temporarily halted and warnings went out over loudspeakers in towns in Hokkaido.
"I was woken by the missile alert on my cellphone," said Ayaka Nishijima, 41, an office worker from Morioka, the capital of Iwate prefecture.
"I didn't feel prepared at all. Even if we get these alerts there's nowhere to run. It's not like we have a basement or bomb shelter, all we can do is get away from the window," she told Reuters by text message.
Some experts said Kim was trying to pressure Washington to the negotiating table with its latest test.
"[North Korea] think that by exhibiting their capability, the path to dialogue will open," Masao Okonogi, professor emeritus at Japan's Keio University, said by phone from Seoul.
"That logic, however, is not understood by the rest of the world, so it's not easy," he said.
In Washington, the Pentagon confirmed the missile flew over Japan but said it did not pose a threat to North America and that it was gathering further information.
Australian Prime Minister Malcolm Turnbull said China, North Korea's main ally and trading partner, needed to do more.
"China has to ratchet up the pressure," Mr Turnbull told Australian radio. "They have condemned these missiles tests like everyone else but with unique leverage comes unique responsibility."
The United States and South Korea are technically still at war with the North because their 1950-53 conflict ended in a truce, not a peace treaty.
- Reuters / RNZ