TOKYO, Japan (AFP) — The United States, Japan and South Korea warned Wednesday that a North Korean nuclear test would warrant an "unprecedentedly strong response," vowing unity after a blitz of missile launches from the hermit state.

Following talks in Tokyo, the three nations' deputy foreign ministers said they would ramp up their deterrence in the region.

"We agreed to further strengthen cooperation … so that North Korea can immediately stop its illegal activities and return to denuclearization talks," said South Korea's Cho Hyun-dong.

"The three countries agreed on the need for an unprecedentedly strong response if North Korea proceeds with its seventh nuclear test," he told reporters.

Japan's Vice-Minister for Foreign Affairs Takeo Mori said North Korea's "intensifying nuclear and missile activities… are a clear and serious challenge to the international community."

"We agreed to ramp up the deterrence in our region with a view towards the denuclearization of North Korea," he said.

Seoul and Washington have repeatedly warned that Pyongyang could be close to testing an atomic bomb for the first time since 2017, after a flurry of ballistic missile launches.

One missile flew over Japan last month, and North Korea has separately claimed to have carried out tactical nuclear drills.

"All of this behavior is reckless and deeply destabilizing," said US Deputy Secretary of State Wendy Sherman, urging North Korea to "refrain from further provocations."