North Korea may have resumed the operation of its reprocessing facilities at Yongbyon to produce nuclear materials, a US think tank suggested Thursday, citing recent satellite imagery.

The thermal infrared imagery of the Yongbyon Nuclear Research Center, taken April 14, provides "strong indications" of activities involving the heating of buildings, said Beyond Parallel, a project of the Center for Strategic and International Studies think tank.

"These indications reveal clear patterns, distinct from the surrounding terrain and daily solar heating patterns, that suggest that the Radiochemistry Laboratory, its associated thermal plant, and the centrifuge plant resumed operations during the early part of March 2021 and have continued into mid-April 2021," it added.

Beyond Parallel earlier suggested possible activities at the North Korean reprocessing facilities, citing satellite imagery taken on March 30, that showed steam or smoke emanating from a Yongbyon facility believed to be a radiochemical laboratory.

The think tank said the new thermal imagery further validated its earlier suspicion.

"Thermal patterns alone may not be able to explain the full extent of the operations by themselves, however, they may (and do in this case) provide clear evidence of operations at these locations," it said.

The reprocessing facilities produce plutonium, a fissile material used to build nuclear bombs.

"As noted in our March 2021 report, this renewed activity is likely an indicator of a new reprocessing campaign designed to expand North Korea's inventory of fissile material for nuclear weapons," said the think tank, calling it a strategic move by North Korean leader Kim Jong-un to continue "slowly ratcheting up pressure" on both South Korea and the United States.

The think tank noted the infrared imagery, however, suggested continued inactivity of the nuclear reactors at Yongbyon, citing the lack of any significant thermal patterns at their locations. (Yonhap)