South Korea has requested the United Nations use its expertise to verify the closure of North Korea's nuclear test site Punggye-ri.

President Moon Jae-in phoned United Nations Secretary General Antonio Guterres on Tuesday to ask for the assistance of the International Atomic Energy Agency (IAEA), UN spokesman Stephane Dujarric said.

The Vienna-based global nuclear watchdog has the capability to confirm whether or not Kim Jong-un follows through on his promise to shut down the launch site at Mount Mantap by the end of May.

Kim revealed his regime would cease operations at the Punggye-ri site, where six nuclear tests have already been carried out, as a gesture of goodwill ahead of the planned total denuclearisation of the peninsula.

Moon also requested the UN help “transform the [Korean] demilitarised zone into a peace zone”, he added.

The progressive dialogue between Kim and Moon at Peace House in the Korean buffer village last week has been commended by Guterres, with the UN head labelling the meeting a “truly historic summit”.

It is understood Guterres is ready to discuss the UN’s involvement, but to what end remains unclear at this stage.

Would the Punggye-ri closure purely symbolic?

Chinese seismologists concluded that the collapse of tunnels at Punggye-ri had effectively forced Kim’s hand to shut down the site.

“It is necessary to continue monitoring possible leaks of radioactive materials caused by the collapse incident,” Wen Lianxing, a geologist with the University of Science and Technology of China in Hefei, said in a statement.

This was backed by a second study, which reported a “chimney” had been created through the collapse which threatened to release radioactive fallout into the air.

A major collapse was said to have occurred days after Pyongyang carried out its largest ever underground nuclear test on September 3. It was reported that 200 workers at the site were killed when a tunnel caved in.

“If reports are true that the tunnels have collapsed, then the test site would be useless for future nuclear tests anyway, so it would just be a symbolic gesture to close it down,” said Duyeon Kim, visiting senior fellow at the Korean Peninsula Future Forum.

“It’s not a serious or sincere gesture to denuclearise.”