Seoul - North Korea appeared to be preparing to launch an intercontinental missile, South Korean media reports said Saturday.

US intelligence services have observed suspicious activity at a missile factory at Sanumdong near the North Korean capital, Pyongyang, the Dong-A Ilbo newspaper said, citing an unnamed informed source.

It appeared that a ballistic missile with a range of more than 5,000 kilometres was being prepared to be transported by train from the site, it reported five days after North Korea conducted its second nuclear test, which was internationally condemned, and afterward carried out six short-range missile launches.

An unnamed informed source also told South Korea's Yonhap News Agency that an intercontinental ballistic missile was recently seen on a cargo train outside Pyongyang and had since been moved to an undisclosed site.

Both reports said the activities observed at the missile factory were similar to ones seen shortly before an April 5 rocket launch by North Korea.

Pyongyang had been repeatedly warned not to carry out the April launch but defied the international community, which said the launch was a test of North Korea's long-range missile technology.

North Korea claimed it was meant to launch a communications satellite. Its neighbours detected no satellite in orbit after the launch, however.

The reports of a potential new launch appeared as tensions rose on the Korean Peninsula after Monday's nuclear test. The UN Security Council and world government criticized the test, and the council was debating punishment of North Korea over it.

In reaction to the council's condemnation Monday - which passed unanimously with the support of North Korea's traditional allies China and Russia - the Stalinist country threatened further nuclear tests and intercontinental missile launches.(dpa)