North Korea has not yet started extracting plutonium for weapons, a news report said on Monday, contradicting what the secretive state said at the weekend that it had resumed nuclear reprocessing.
"There was no evidence yet that North Korea has earnestly started reprocessing," the Chosun Ilbo newspaper quoted a government source as saying. There are workers near the facility who appear to be cleaning and doing maintenance, the source said.
North Korea said on Saturday it had started to extract plutonium from spent fuel rods at its Yongbyon nuclear arms plant, further raising regional tensions already stoked by its defiant rocket launch this month.
The announcement came hours after a UN Security Council committee on Friday placed three North Korean companies on a UN blacklist for aiding Pyongyang's missile and nuclear programmes, eliciting a sharp rebuke from a North Korean envoy.
Market players, used to the North's threats, on Monday ignored the latest development. But the move could increase the regional security threat because Pyongyang would add to its meagre stockpile of fissile material, increasing the likelihood of another nuclear weapons test.
Experts said it could take North Korea, which conducted its only nuclear test in October 2006, at least three months to have the reprocessing facility up and running again.
The nuclear fuel reprocessing plant is one of the facilities at the North's Yongbyon nuclear complex about 100 km (60 miles) north of the capital, Pyongyang, which has been disabled under an aid-for-disarmament deal with five other countries.
Experts said North Korea, which has enough fissile material for six to eight nuclear bombs, would likely be able to extract enough material for one more bomb by separating plutonium from spent fuel rods cooling at the plant.
North Korea has said it was quitting the six-way talks with the South, the United States, Japan, Russia and China in anger over UN Security Council measures to punish it for the April 5 launch, widely seen as a disguised long-range missile test that violated UN sanctions.
It has also expelled UN inspectors overseeing steps to put the entire Yongbyon plant out of operation for at least a year.