SEOUL, South Korea -- The United States has given South Korea a satellite photograph showing smoke coming from a North Korean nuclear facility, a possible sign the communist nation has started reprocessing spent fuel rods, a South Korean official said Thursday.
Reprocessing the rods would be a key step toward producing nuclear weapons.
The official, who spoke on condition of anonymity, said other signs of nuclear activity, such as traces of chemicals used in reprocessing or heat signatures, had not been detected from the Yongbyon nuclear complex. He said the smoke was coming from radiation and chemical laboratories in the facility.
During nuclear talks in Beijing last month, U.S. officials said North Korea claimed it had reprocessed 8,000 spent nuclear fuel rods -- a move that could yield several atomic bombs within months.
However, U.S. and South Korean officials said they could not verify the claim and suggested North Korea may be bluffing in an attempt to increase its leverage in talks with the United States over its suspected nuclear weapons programs.
South Korean President Roh Moo-hyun travels to the U.S. on Sunday to meet President Bush. They are to discuss a North Korean proposal in which Pyongyang is believed to offer to end its nuclear activities in exchange for economic aid and a security guarantee from Washington.
A spokesman for South Korea's Unification Ministry, Kim Jung-ro, said Thursday that the renewed activity at Yongbyon did not necessarily mean the North was reprocessing.
More evidence needed
"We are not sure if they are doing it as an extension of the bluffing or if it is a step to develop nuclear weapons. We need more evidence," he said.
In a letter to his armed forces chiefs, South Korea's Defense Minister Cho Young-gil said "possibilities of North Korea committing various provocations to raise its negotiating power is rising."
Cho called for heightened surveillance and vigilance in the lette published in the Defense Ministry's newspaper on Thursday.
"South Korea and the United States, under the principle of peacefully resolving the North Korean nuclear issue, have tried to solve the problem through dialogue," he said.
"But if North Korea's aim is achieving nuclear weapons itself, the possibility of a diplomatic resolution could inevitably be limited," he said.
Tension over the nuclear dispute spiked last month during the Beijing talks, when, according to U.S. officials, North Korea claimed to have nuclear weapons and threatened to use or export them, depending on U.S. actions.
The talks were the first since the crisis flared in October, when Washington said North Korea admitted running a secret nuclear weapons program in violation of a 1994 treaty.