On Thursday, March 25, two ballistic miles were launched into the Sea of Japan by North Korea just days after the country fired two non-ballistic missiles into the Yellow Sea.
Ballistic missiles are considered to be threatening under United Nations (UN) Security Council regulations, and North Korea is banned from firing them.
Why have the missiles been fired - and have they done any damage?
Firing non-ballistic missiles - like the ones fired by North Korea on Tuesday, March 23 - is not considered a violation of UN security sanctions.
The firing of longer-range ballistic missiles, however, is considered a violation of these sanctions and may be considered a provocation by neighbouring countries like Japan as well as western countries like the US.
According to Japanese officials, North Korea fired the missiles after 07:00 local time on Thursday.
They flew 430km and 420km respectively before they landed in waters outside of Japan’s exclusive economic zone.
It is not clear why North Korea has launched the ballistic missiles, though past launches suggest that such behaviour is a way of the country demonstrating its military power to the rest of the world.
The US Pacific Command, however, which oversees military forces in the Asia-Pacific region, said the test showed "the threat that North Korea's illicit weapons programme poses to its neighbours and the international community".
Japan confirmed after Thursday’s launch that debris had fallen into the sea with no damage on land.
How often do North Korea fire missiles?
This is not the first time North Korea has fired missiles into neighbouring territory or tested other weapons.
The last time the country fired ballistic missiles was around this time last year, on March 2, when two ballistic missiles were fired into the Sea of Japan.
Tensions became extremely heated between the US and North Korea during 2017 after the latter tested a series of nuclear and missile tests.
Was the test legal?
The testing of ballistic missiles contravenes UN Security Resolutions, which ban North Korea from conducting such tests.
However, North Korea has in the past rejected UN resolutions as themselves “illegal”, so it is unlikely the country will consider their latest test to be “illegal”.
In 2018, President Trump and North Korean leader Kim Jong-un reached a deal in which it was promised North Korea would not test nuclear weapons or long-range ballistic missiles.
How have world leaders reacted?
Following North Korea’s launch of non-ballistic missiles on Tuesday, President Biden said the move was “not a provocation” as it did not contravene UN resolutions.
The most recent launch, however, may prompt a response from officials in the west.
So far, President Biden has not commented on the most recent launch.
The Biden administration says it has tried to make diplomatic contact with North Korea since President Biden took office, but has seen no response.
North Korean officials are yet to recognise the new president, and relations between both countries remain tense.