North Korea appears to be still expanding operations at its main nuclear site, the UN atomic watchdog indicates.
The statement by the head of the International Atomic Energy Agency on Thursday is a further sign that North Korea is pressing ahead with its atomic activities despite pressure from the United States for it to scrap its nuclear weapons program.
At a leaders' summit in June both sides pledged to work towards the complete denuclearisation of the Korean Peninsula.
Since then, few concrete steps have been made towards the full and irreversible dismantling of North Korea's nuclear arms program that Washington has called for.
At Yongbyon, North Korea's main nuclear facility which is widely believed to have provided fissile material for its bombs, components appear to have been brought into a light-water reactor being built there, IAEA chief Yukiya Amano said.
"At the light water reactor, the agency also observed activities consistent with the fabrication of reactor components and the possible transfer of these components into the reactor building," Amano said in a statement to the IAEA's board of governors, reporting on the period since August.
The IAEA has not had access to North Korea since 2009 and mainly monitors activities there through satellite imagery, meaning it cannot confirm its observations.
North Korea also appeared to have continued work at the nearby Kuryong River that it dammed last year to increase the supply of water available for cooling the planned reactor or the existing experimental one, which has an output capacity of 5 megawatts.
"Further activities were observed near the Kuryong River. These may be related to changes to the cooling infrastructure for the 5MW(e) reactor and the light water reactor," Amano said, adding that the experimental reactor was likely shut down while some of those unspecified activities were carried out.
Amano referred to a meeting between North and South Korea in September at which the North expressed its readiness to take measures including a permanent dismantlement of its main nuclear facilities in Yongbyon should there be unspecified corresponding action from the United States.
