South Korean President Moon Jae-in has asked the United Nations to verify the planned closure of North Korea's nuclear test site, a UN spokesman said Tuesday.

Moon made the request in a phone call to UN Secretary-General Antonio Guterres on Monday, a few days after North Korean leader Kim Jong Un told the South Korean leader he planned to shut down the test site in May.

"The president sought the support of the United Nations to verify the imminent closure of the DPRK's nuclear test site, as announced by the DPRK Chairman Kim Jong Un," said UN spokesman Stephane Dujarric. The Democratic People's Republic of Korea (DPRK) is North Korea's official name.

Moon also asked for UN support to "transform the demilitarized zone into a peace zone" between the two Koreas, he added.

Guterres said the United Nations was ready to discuss possible forms of support, but no details were provided.

The Vienna-based International Atomic Energy Agency (IAEA), the UN's global nuclear watchdog, has the expertise to carry out verification missions.

Kim told Moon during the summit on Friday that he planned to dismantle the Punggye-ri nuclear test site as the leaders pledged to pursue a permanent peace treaty and denuclearize the Korean peninsula.

The Security Council has imposed tough economic sanctions on North Korea after Pyongyang last year carried out a sixth nuclear test and a series of advanced missile launches.

Guterres on Friday applauded the "truly historic summit" between the Korean leaders and urged them to quickly turn their commitments into action. (AFP)