A North Korean organisation demanded Thursday that the United States be "beaten to death" like a "rabid dog" for spearheading fresh UN sanctions on Pyongyang over its latest nuclear test, adding ally Japan should be "sunken into the sea".

The UN Security Council unanimously imposed an eighth set of sanctions on the North Monday, banning it from trading in textiles and restricting its oil imports, a week after Pyongyang tested what it said was a hydrogen bomb small enough to fit onto a missile, raising tensions on the peninsula.

A spokesman for the North's Korea Asia-Pacific Peace Committee (KAPPC) denounced the "heinous sanctions resolution" and said there were mounting calls for strong retaliation against the US and its allies.

"The army and people of the DPRK are unanimously demanding that the Yankees, chief culprit in cooking up the 'sanctions resolution', be beaten to death as a stick is fit for a rabid dog," he said in a statement carried by the official KCNA news agency.

"Now is the time to annihilate the US imperialist aggressors. Let's reduce the US mainland into ashes and darkness," it said.

North Korea has a long history of issuing dramatic threats against the US and its allies but not carrying them out.

According to the South's unification ministry, the KAPPC acts as "a window for improving relations with countries like the US and Japan... while campaigning to change North Korea's closed and negative image".

But the KAPPC statement accused Tokyo of "dancing to the tune of the US" and warned of a "telling blow" against Japan, noting the missile test that overflew the Asian island nation last month.

The North's launch of an intermediate range missile over Hokkaido triggered alarm bells, sparking emergency sirens and mass text alerts in northern Japan.

"The four islands of the archipelago should be sunken into the sea by the nuclear bomb of Juche," KAPPC warned, referring to the North's national philosophy of "Juche" or self-reliance.

North Korea says it needs nuclear weapons to protect itself from "hostile" US forces.

Experts believe Pyongyang's weapons programme has made rapid progress under leader Kim Jong-Un, with previous sanctions having done little to deter it.