Spy satellites have captured images that appear to show North Korea making preparations to move a long-range missile from a weapons factory to a launch pad in the country's northeast, a South Korean official said Saturday.
The images appear to show preparations to move the missile via train from the factory near Pyongyang to the Musudan-ni launch site, said the official, who spoke on condition of anonymity because he is not authorized to speak on intelligence matters.
Preparations to launch such a missile would take about two weeks, South Korea's Yonhap news agency quoted the official as saying.
The agency said the missile's size was comparable to a long-range rocket that North Korea tested in April.
It is believed that it has a range of more than 6,700 kilometres, which means it could travel as far as Alaska.
On Friday, U.S. officials said they noticed increased activity at the launch site, but provided no details about what they saw.
The new developments come as U.S. Defence Secretary Robert Gates ratcheted up the rhetoric against North Korea, saying the isolated state must face tougher sanctions from its neighbours in Asia.
Gates said the U.S. is tired of North Korea threatening nuclear war to gain aid and other concessions before then reneging on promises to scale back its nuclear plans.
"They create a crisis and the rest of us pay the price to return to the status quo ante," Gates told the Shangri-La Dialogue, an annual meeting of defence and security officials. "As the expression goes in the U.S., I'm tired of buying the same horse twice."
"There are other ways perhaps to get the North Koreans to change their approach," Gates added. "I think this notion that we buy our way back to the status quo ante is an approach that I personally at least think we ought to think very hard about."
North Korea has spent the last five days testing its nuclear weapon capability, including test-launching six short-range missiles.
The show of force has been accompanied by statements that the North will no longer honour the 1953 armistice it signed with South Korea.
On Saturday, North Korea called last Monday's nuclear test an act of self defence.
The Korean Central News Agency said the communist state "will deal decisive and merciless blows at the enemies who desperately run amok to dare pre-empt an attack on it."
The UN Security Council is drafting military and financial sanctions against North Korean in response to the testing. However, similar sanctions in 2006 were not enforced and were largely ignored by North Korea's allies, Russia and China.
On Friday, The Associated Press obtained excerpts of a draft resolution, which calls for the 2006 sanctions to be enforced. These include a partial arms embargo, a ban on luxury goods and ship searches for illegal weapons.
Later Saturday, defence officials from the U.S., Japan and South Korea also met to discuss possible sanctions.
"North Korea perhaps to this point may have mistakenly believed that it could be perhaps rewarded for its wrong behaviours," Lee told reporters. "But that is no longer the case."
With files from The Associated Press
