South Korea plans to send a special envoy to North Korea in response to an invitation from leader Kim Jong-un, South Korean President Moon Jae-in told his US counterpart Donald Trump in a phone call on Thursday.

The two presidents discussed the recent visits to the south by high-level North Korean officials, the South Korean presidential Blue House said in a statement.

The Olympics gave a boost to recent engagement between the two Koreas after more than a year of sharply rising tensions over the North’s missile programme and its sixth and largest nuclear test in defiance of UN sanctions.

"[Mr Moon and Mr Trump] agreed to continue to make efforts to head toward the Korean peninsula's denuclearisation by maintaining the momentum of South-North dialogue," the Blue House statement said.

In sending an envoy to Pyongyang, Mr Moon said he would be seeking to reciprocate for the senior delegations dispatched to the Olympics by Kim Jong-un, including his sister, Kim Yo-jong, the first visit by a member of the North’s ruling bloodline since the 1950-53 Korean War.