North Korea is "rapidly expanding" its nuclear reactor as revealed in new satellite images as global tensions rise following its most recent missile test.
The Yongbyon Nuclear Research Facility has previously been dormant but new images show it is being renovated - a sign North Korean leader Kim Jong-un is preparing to bolster production.
The 5-megawatt reactor was believed to have been inactive since 2018 as talks between Pyongyang and Washington have become frosty.
Satellite images show construction at the plant, which could increase North Korea's nuclear material by 25 per cent.
The reactor produces plutonium, one of the two ingredients needed to build nuclear weapons along with highly enriched uranium.
In 2019, the North Korean leader Kim Jong-un had offered to dismantle part of the Yongbyon complex at a second summit with former President Donald Trump but not other sites, in exchange for sanctions relief - and was rejected.
Jeffrey Lewis, a weapons expert and professor at the Middlebury Institute of International Studies, told CNN : "The most recent expansion at Yongbyon probably reflects plans to increase production of nuclear materials for weapons production.
"The new area is approximately 1,000 square meters, enough space to house 1,000 additional centrifuges. The addition of 1,000 new centrifuges would increase the plant's capacity to produce highly enriched uranium by 25 per cent.
He added that construction is consistent with earlier efforts to add floor space to allow for more centrifuges and enrich a larger quantity of uranium.
The professor said if the country also upgrades the centrifuges currently being used at the complex, it "could increase the capacity of the plant substantially".
US officials are aware of the construction at the plant and admit it could signal plans to increase stock, sources say.
North Korea's state media has also accused the US of double standards over military activities and pursuing a hostile policy towards Pyongyang.
Earlier this week, North Korea said it has successfully completed a test-fire for a new type of long-range cruise missile.
According to the secretive regime's state media on Monday the missile flew 930 miles before hitting its target.
The weapons landed into the country's own territorial waters with tests carried out on Saturday and Sunday, according to KCNA.
It was seen as the North's first missile launch after it tested a new tactical short-range ballistic missile in March.
North Korea also conducted a cruise missile test just hours after US President Joe Biden took office in late January.
The latest test highlighted progress in Pyongyang's weapons programme amid gridlock over talks aimed at dismantling the North's nuclear and ballistic missile programmes in return for U.S. sanctions relief.
Those talks have stalled since 2019.
Rodong Sinmun, the ruling Workers' Party's official newspaper, published photos of the new long-range cruise missile flying and being fired from a transporter-erector-launcher.
The missile is a strategic weapon that has been developed over the past two years and a key element of a five-year plan outlined in January to advance defence science and arsenals, KCNA said.
The test provides "strategic significance of possessing another effective deterrence means for more reliably guaranteeing the security of our state and strongly containing the military manoeuvres of the hostile forces," KCNA said.
"In this course, detailed tests of missile parts, scores of engine ground thrust tests, various flight tests, control and guidance tests, warhead power tests etc. were conducted with success."
