Flags of North Korea (rear) and South Korea (front) are seen from the border area between two Koreas in Paju, South Korea, on Tuesday. AP

Speaking at a wide-ranging news conference to mark his first 100 days in office, Yoon made no mention of the launches, which were only publicly reported later by the South Korean military.

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Yoon repeated his willingness to provide phased economic aid to North Korea if it ended nuclear weapons development and began denuclearisation, noting that he had called for a dialogue with Pyongyang since his campaign.

President Yoon Suk Yeol delivers a speech during a news conference in Seoul, South Korea, on Wednesday. AP

"Any dialogue between the leaders of the South and North, or negotiations between working-level officials, should not be a political show, but should contribute to establishing substantive peace on the Korean peninsula and in Northeast Asia," he said.

The comments were an apparent criticism of summits involving his predecessor Moon Jae-in, North Korean leader Kim Jong Un, and then-US President Donald Trump.

Despite those meetings, denuclearisation talks stalled in 2019 and North Korea has said it will not trade away its self-defence, though it has called for an end to sanctions. It has been observed preparing for a possible nuclear test, which would be its first since 2017.

North Korea's launches on Wednesday were the first reported in months, and come a day after South Korea and the United States began preliminary joint drills ahead of a restart of live field training halted under Moon.

North Korean leader Kim Jong Un attends a meeting. File photo

Yoon said South Korea was not in a position to guarantee the North's security if it gave up its nuclear weapons, but Seoul did not want a forced change in the status quo in the North.

The North's recent missile tests and nuclear development has revived debate over whether the South should pursue its own nuclear weapons. Yoon said that he was committed to the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) and working with the United States to boost its "extended deterrence" for South Korea.

"The NPT should not be abandoned and I will adhere to that until the end," he said.

Reuters