North Korean leader Kim Jong-un hosted a huge celebration to congratulate his nuclear scientists and technicians who steered the country’s sixth and largest nuclear test a week ago, its official news agency said on Sunday.

News of the celebration comes as the UN secretary general, Antonio Guterres, said in an interview published Sunday the showdown over North Korea’s nuclear and missile programme was the world’s worst crisis “in years”.

South Korea had been bracing for another long-range missile launch in time for the 69th anniversary of North Korea’s founding on Saturday, but no fresh provocations were spotted.



Instead, amid numerous events in the country, Kim threw a banquet topped with an art performance and a photo session with the leader himself, the official agency KCNA said. KCNA did not specify when the banquet had been held, but analysts said it had likely been on Saturday.

Kim Jong-un is congratulated by North Korea’s elite at an event to mark the latest nuclear test and the country’s 69th anniversary. Photograph: STR/AFP/Getty Images

Photos released on Sunday by KCNA showed the young leader breaking into a broad smile at the people’s theatre in Pyongyang with two prominent scientists: Ri Hong-sop, head of North Korea’s nuclear weapons institute, and Hong Sung-mu, deputy director of the munitions industry department. Ri is a former director of the Yongbyon nuclear research centre, North Korea’s main nuclear facility north of Pyongyang, where Hong also worked as a chief engineer.

North Korea had said the latest test was an advanced hydrogen bomb. There was no independent confirmation but some western experts said there was enough strong evidence to suggest the reclusive state has either developed a hydrogen bomb or was getting very close.

KCNA said on Sunday the scientists and technicians “brought the great auspicious event in national history, an extra-large event through the perfect success in the test of H-bomb”. Kim praised the developers in his own remarks as “taking the lead” in attaining the “final goal of completing the state nuclear force” in line with his parallel pursuit of nuclear and economic development.

“The recent test of the H-bomb is the great victory won by the Korean people at the cost of their blood while tightening their belts in the arduous period,” Kim was quoted as saying.

Ri and Hong’s roles have also been noted overseas, prompting the UN, the US and South Korea to blacklist them.

North Korean leader Kim Jong-un watches the celebrations with his wife, Ri Sol-ju. Photograph: STR/AFP/Getty Images

In an interview published by the French Sunday newspaper Le Journal du Dimanche, Guterres said “it’s the most serious [crisis] that we have had to face in years”, admitting he was “very worried”.

“To date, we have had wars which have been initiated after a well thought-out decision,” he said. “But we also know that other conflicts have started through an escalation caused by sleepwalking. We have to hope that the seriousness of this threat puts us on the path of reason before it is too late.”

Guterres said the key question was to get North Korea to stop its nuclear and ballistic missile programme and respect UN security council resolutions.

“But we must also maintain the unity of the security council at all costs, because it is the only tool which can carry out a diplomatic initiative with a chance of success,” he said.

The US wants the security council to vote on Monday to impose tougher sanctions against Pyongyang, despite resistance from China and Russia.

A US-presented draft resolution calls for an oil embargo on North Korea, an assets freeze on Kim, a ban on textiles and an end to payments of North Korean guest workers.

Russia and China are believed to be opposed to the measures as a whole, except for the ban on textiles, during a meeting of experts Friday.

The Japanese defence minister, Itsunori Onodera, said it was vital to put pressure on North Korea through additional sanctions, including blocking or slowing its fuel supplies.

“If we put firm pressure on North Korea such that it realises it cannot develop missiles, it will accept dialogue and we can progress with diplomatic efforts,” Onodera told public broadcaster NHK on Sunday. “Unless we firmly apply pressure, North Korea will not change its direction.”