SEOUL/WASHINGTON • North Korea showed trademark defiance yesterday over new United Nations sanctions imposed after its sixth and largest nuclear test, vowing to redouble efforts to fight off what it said was the threat of a United States invasion.

US President Donald Trump said Monday's sanctions, unanimously agreed by the 15-member UN Security Council, were just a small step towards what is ultimately needed to rein in Pyongyang over its nuclear and missile programmes.

The North's Foreign Ministry said the resolutions were an infringement on its legitimate right to self-defence and aimed at "completely suffocating its state and people through full-scale economic blockade".

"The DPRK will redouble the efforts to increase its strength to safeguard the country's sovereignty and right to existence and to preserve peace and security of the region by establishing the practical equilibrium with the US," it said in a statement carried by the official KCNA news agency, using North Korea's official name. The statement echoed comments on Tuesday by the North's Ambassador to the UN Han Tae Song.

The North's Rodong Sinmun newspaper also accused South Korea of being Washington's puppet, criticising Seoul's agreement with the US to amend an existing bilateral guideline that will now allow the South to use unlimited warhead payloads on its missiles.

The UN Security Council agreed to boost sanctions against North Korea, banning its textile exports and capping fuel supplies, and making it illegal for foreign firms to form commercial joint ventures with North Korean entities.

The UN resolution was triggered by North Korea's Sept 3 test of what it said was a hydrogen bomb.

Yesterday, South Korea said its land-based xenon detector in the north-eastern part of the country as well as mobile equipment off the east coast had found traces of xenon-133 isotope.

Xenon is a naturally occurring, colourless gas used in manufacturing of some types of lights. But the detected xenon-133 is a radioactive isotope that does not occur naturally and which has been linked to North Korea's nuclear tests in the past.

South Korea said the xenon traces detected had no impact on its environment and population.

REUTERS