North Korea claims it has miniaturised nuclear warheads

North Korea’s leader Kim Jong-un says his country has nuclear warheads small enough to be mounted on ballistic missiles, in the latest claim that the isolated state has significantly advanced its atomic weapons capabilities.

The North's daily Rodong Sinmun ran photos of Mr Kim meeting a group of nuclear scientists and technicians, which showed him standing beside what looked like a miniaturised nuclear device, a small, stainless steel globe on a low table, while behind him stands a ballistic missile.

The Korean Central News Agency (KCNA) quoted Mr Kim as saying that his country has made a nuclear bomb lighter and achieved its “standardisation.”

“The nuclear warheads have been standardised to be fit for ballistic missiles by miniaturising them,” Mr Kim was quoted as saying by the KCNA. “This can be called true nuclear deterrent.”

He also inspected the nuclear warheads designed for thermonuclear reaction, KCNA said, referring to a hydrogen bomb that the country claimed to have tested in January.

Western experts doubt that the North, or the Democratic People’s Republic of Korea (DPRK) as it is officially known, has the capability to miniaturise nuclear devices to fit on a missile nor has it developed thermonuclear devices.

North Korea has been in defiant mood, cranking up the belligerent rhetoric since the UN Security Council’s adoption of its toughest ever sanctions against Pyongyang over its fourth nuclear test and rocket launch.

“It was very rare that the North’s leader has come to the front in displaying his country’s nuclear capabilities,” Chang Yong-seok, a researcher at the Seoul National University Institute for Peace and Unification Studies, told the Yonhap news agency.

The North’s reaction seems to indicate that the country’s regime views the Seoul-Washington joint exercise as “very grave”, he said.

Meanwhile, Russia, has described “totally unacceptable” North Korea’s threats to launch pre-emptive nuclear strikes against South Korea and the United States, and called for restraint, after South Korea and the US began annual, large-scale military drills, which usually anger Pyongyang.

“Pyongyang must realise that in doing so, North Korea is definitively turning its back on the international community and creating a legal basis for the use of military force against it,” the Russian foreign ministry said in a statement.

A UN panel set up to monitor sanctions under an earlier Security Council resolution adopted in 2009 has raised “serious questions” about how effective sanctions are, because of “the low level of implementation of Security Council resolutions by member states.”