North Korea has come out fighting following fresh UN Security Council sanctions on Pyongyang and after the United States and South Korea celebrated the punishing measures.

North Korea on Monday condemned the sanctions imposed in response to its weapons programmes, saying it would not negotiate over nuclear arms while threatened by the US.

The sanctions passed at the weekend were a “violent violation of our sovereignty”, Pyongyang said in a statement carried by its official Korean Central News Agency, adding it would take “righteous action” in return.

“We will not put our self-defensive nuclear deterrent on the negotiating table” while it faced threats from Washington, it said, “and will never take a single step back from strengthening our nuclear might”.

The UN Security Council unanimously adopted on Saturday a US-led resolution, which bans mineral and seafood exports from North Korea worth more than $1bn.

The triggering event late July, North Korea’s latest test of ballistic missiles, had the international community and experts concerned. Along with the North Korean government, they say the missiles can reach different parts of the US.

News of the brief encounter between the Koreas came as Moon Jae-In, South Korea’s president, and his US counterpart, Donald Trump, agreed to apply maximum pressure on North Korea.

Moon told Trump that South Korea “cannot let another war to break out” on the peninsula after the 1950-53 Korean War that sealed the division of two Koreas, the presidential Blue House said in a statement.

Even a conventional conflict on the peninsula could cost a million dead or wounded within months, estimates say.