In reaction to the latest sanctions imposed by the United Nations (UN) on North Korea over its recent nuclear test, Pyongyang maintained defiance and vowed to increase efforts to fight off a perceived invasion threat from the United States.

The United Nations Security Council (UNSC) on Monday unanimously passed new sanctions against North Korea, which has banned textile exports and restricted shipments of oil products to Pyongyang.

US President Donald Trump on Tuesday said the sanctions agreed by the 15-member UNSC were just a small step towards what is needed to rein in Pyongyang over its burgeoning nuclear weapons programme.

The fresh sanctions were imposed against the Korean nation as it claimed to have successfully tested a hydrogen bomb — the sixth nuclear test carried out by the country and its largest — which possibly triggered a 6.3-magnitude artificial earthquake.

The hydrogen bomb test reportedly produced an explosion nearly 10 times larger than the blast from the Hiroshima bomb in 1945. The test spurred global concern that Pyongyang may be planning more such tests.

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

"The DPRK (Democratic People's Republic of Korea) 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," the Ministry said in a statement carried by the state's official KCNA news agency.

The statements from the North Korea's Foreign Ministry echoed the sentiments sounded by the ambassador to the UN, Han Tae Song, who said Pyongyang was "ready to use a form of ultimate means".

"The forthcoming measures ... will make the US suffer the greatest pain it ever experienced in its history," Han said.

The North Korean paper Rodong Sinmun on Wednesday accused South Korea of being America's "puppet", denouncing the South's deal with the US to amend an existing bilateral guideline which will now allow the South to use unlimited warhead payloads on its missiles.