North Korea could conduct a seventh nuclear test "at any time", a US official has warned.

Sung Kim, US special representative to North Korea, made the warning days after Pyongyang test-launched a record eight ballistic missiles on Sunday.

Any such nuclear test would be met with a "swift and forceful response", US Deputy Secretary of State Wendy Sherman told reporters.

Pyongyang has not carried out a nuclear test for five years.

However, tensions have been rising on the Korean peninsula. Speaking from Jakarta, Mr Kim said North Korea had tested an unprecedented number of missiles this year - 31 compared to 25 during the whole of its last record-breaking year, 2019.

"And it's only June," he told reporters during a briefing in Jakarta, Indonesia.