North Korea has fired two ballistic missiles into the Sea of Japan, says the US and Japan - the first such test since Joe Biden became US president.
Pyongyang is banned from testing ballistic missiles, considered threatening weapons, under UN Security Council resolutions.
Both Japan and South Korea have condemned the test.
It comes just days after North Korea reportedly fired two non-ballistic missiles into the Yellow Sea.
Japan said no debris had fallen within its territorial waters.
The US Pacific Command, which oversees military forces in the Asia-Pacific region, said on Thursday that the test highlighted "the threat that North Korea's illicit weapons programme poses to its neighbours and the international community".
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Mr Biden is yet to officially comment.
On Tuesday, he played down a non-ballistic missile launch which took place over the weekend, saying the US did not consider it a provocation. Those short-range missiles were thought to be either artillery or cruise missiles, which are not banned under the UN Security Council resolutions on North Korea.
Thursday's test also comes days after the US received its first North Korean in custody after Mun Chol Myung was extradited from Malaysia. Mr Mun is a businessman accused of laundering money through the US financial system to provide luxury items to North Korea.
The incident angered North Korea so much it cut off diplomatic ties with Malaysia.
The test at the weekend of either artillery or cruise missiles can be shrugged off. But this ballistic missile test is a clear violation of United Nations Security sanctions.
Having said that, Mr Biden's predecessor Donald Trump did wave off any questions regarding similar weapons tests in 2019.
The deal between Mr Trump and Kim Jong-un reached in Singapore in 2018 was that Pyongyang would not test long-range ballistic missiles or nuclear weapons.
At that time, the White House did not concern itself with smaller tests.
But Mr Biden's team is just back from Japan and South Korea, and promised that "America was back" and supporting its allies.
Perhaps then, the administration will have to say something about a weapons test which threatens its friends in North East Asia.
Washington will also be aware that Pyongyang has bigger weapons in its arsenal which it has not tested since late 2017.
North Korea has spent more than a year in isolation. It even cut off most trade with its closest ally China amidst the Covid-19 pandemic, and its economy is thought to be in a dire state.
Now that the weapons tests appear to be making a return, many are wondering just how far is Kim Jong-un willing to go to get the attention of the White House.
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Japanese officials said North Korea fired the two missiles after 07:00 local time on Thursday (20:00 GMT Wednesday). They flew 420km and 430km respectively before landing in waters outside of Japan's exclusive economic zone. There was no damage inflicted to ships or aeroplanes.
North Korea last fired ballistic missiles a year ago amid stalled relations between then-US President Donald Trump and North Korean leader Kim Jong-un.
The Biden administration says it has unsuccessfully tried to make diplomatic contact with North Korea.
Pyongyang has yet to acknowledge that Mr Biden is now in office, and the two countries remain at loggerheads over the North's nuclear and ballistic missile programmes.
Despite two summits in 2018 and 2019, and then a historic meeting at the Korean border, the future of the US-North Korea talks look bleak.
Here's an overview of a saga that has at times threatened nuclear war.
Why did North Korea develop nuclear weapons?
The Korean peninsula was divided after World War Two and the North developed an authoritarian form of government.
Isolated globally, it saw nuclear weapons as a deterrent against a world it believed was seeking to destroy it.
Could it carry out a nuclear attack?
Probably. Pyongyang has carried out six nuclear tests.
It claims, though this remains unverified, to have developed a nuclear bomb small enough for a long-range missile.
It also has a ballistic missile experts believe could reach the US, and in 2019 tested a missile that could carry a nuclear weapon and be launched from a submarine.
At the start of 2020, Kim Jong-un ended the country's moratorium on nuclear testing.
How did talks begin?
After months of escalating mutual threats, in January 2018 Mr Kim said he was "open to dialogue".
Mr Trump accepted, ignoring past pre-talk conditions that North Korea denuclearise first.
On 12 June 2018, Mr Trump became the first sitting president to meet a North Korean leader.
The two signed an agreement committing to the "complete denuclearisation of the Korean peninsula" but with no detail on what that meant.
Back to stalemate?
Since then, there has been little progress, despite more talks.
The US wants North Korea to unilaterally give up its nuclear weapons while Pyongyang wants a step-by-step approach to ease the crippling sanctions regime.
The most recent talks between officials, though not leaders, took place in Sweden in October 2019.
The US said "good discussions were had" but North Korea said the US "brought nothing to the negotiation table".
Since then, North Korea has continued missile testing., while the US has urged Pyongyang to resume talks.
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