North Korea has officially enshrined the right to use preemptive nuclear strikes to protect itself in a new law that leader Kim Jong Un said makes its nuclear status "irreversible" and bars denuclearisation talks, state media reported on Friday.

The move comes as observers say North Korea appears to be preparing to resume nuclear testing for the first time since 2017, after historic summits with then-US President Donald Trump and other world leaders in 2018 failed to persuade Kim to abandon his weapons development.

The North's rubber-stamp parliament, the Supreme People's Assembly, passed the legislation on Thursday as a replacement to a 2013 law that first outlined the country's nuclear status, according to state news agency KCNA.

"The utmost significance of legislating nuclear weapons policy is to draw an irretrievable line so that there can be no bargaining over our nuclear weapons," Kim said in a speech to the assembly, adding that he would never surrender the weapons even if the country faced 100 years of sanctions.

Among the scenarios that could trigger a nuclear attack would be the threat of an imminent nuclear strike; if the country's leadership, people or existence were under threat; or to gain the upper hand during a war, among other reasons.

A deputy at the assembly said the law would serve as a powerful legal guarantee for consolidating North Korea's position as a nuclear weapons state and ensuring the "transparent, consistent and standard character" of its nuclear policy, KCNA reported. (Reuters)