North Korea has conducted a "crucial test" at a satellite launch site to boost its nuclear deterrent, state media reports.
A spokesman told KNCA news agency it took place late on Friday at the Sohae Satellite Launching Ground, but did not give specific details.
Talks between the US and North Korea about its nuclear programme remain stalled.
US President Donald Trump has refused to lift biting sanctions until North Korea fully abandons its nuclear programme.
But leader Kim Jong-un has instead been asking for new concessions from the US by the end of the year.
Pyongyang has said it will adopt a "new way" if that does not happen – saying the US can expect an ominous "Christmas gift" if it does not comply.
What was the test?
It is not clear exactly what North Korea tested at the site.
Ankit Panda, North Korea expert at the Federation of American Scientists, told the BBC it could be a ground test for a ballistic missile engine. South Korea's defence minister had previously said this was the purpose of the test earlier in December.
North Korea has stepped up its weapons tests and its strong rhetoric in recent weeks.
Japan condemned the country for "repeated launches of ballistic missiles" after two projectiles were fired in November.
The North however said it was testing a "super-large multiple-rocket launcher", and threatened that Japan "may see what a real ballistic missile is in the not distant future".
Why is North Korea conducting a test now?
The test comes amid heightening tensions in the region.
The UN Security Council met on Wednesday at the request of the US to discuss North Korea's weapons programme – a move North Korea called a "serious provocation".
And on Sunday, US Special Representative for North Korea Stephen Biegun plans to visit South Korean capital Seoul. US President Donald Trump has said he still hopes to reach an agreement with North Korea.