Pyongyang has also been conducting ‘operational tests’ of a nuclear detonation device, SEOUL: North Korea fired a volley of missiles Wednesday, including possibly its largest intercontinental ballistic missile, just hours after US President Joe Biden left Asia after a trip overshadowed by Pyongyang’s sabre-rattling. North Korea has also been conducting “operational tests” of a nuclear detonation device, Kim Tae-hyo, Seoul’s first deputy director of the National Security Office, said, adding a test could come “imminently.” His warning adds to the drumbeat of predictions from US and South Korean officials, who have been saying for weeks that Kim Jong Un’s regime is close to conducting its seventh nuclear test. Three missiles, including one ICBM, were fired from the Sunan area in Pyongyang, Seoul said — one of nearly 20 weapons tests by North Korea so far this year — prompting joint US-South Korea live fire missile drills in response. Pyongyang’s missile launches are “an illegal act in direct violation of UN Security Council resolutions,” Seoul’s government said after a National Security Council meeting chaired by President Yoon Suk-yeol. The United States called for Pyongyang to “engage in sustained and substantive dialogue,” a state department spokesman said. The three early morning ballistic missile launches came within an hour of each other, South Korea’s Joint Chiefs of Staff said in a statement. “The first ballistic missile (suspected ICBM) had a range of around 360 kilometers (225 miles) and an altitude of around 540km,” Seoul’s Joint Chiefs of Staff said in a statement. This could have been North Korea’s largest ICBM, the Hwasong-17, Kim Tae-hyo said later. The second ballistic missile “disappeared at an altitude of 20km” and the third — a suspected short-range ballistic missile — traveled around 760km at an altitude of around 60km. The Wednesday launches are the latest in a blitz of sanctions-busting weapons tests by Pyongyang this year, including test-firing intercontinental ballistic missiles at full range for the first time since 2017. The latest apparent test come just days after Biden left South Korea Sunday. The tests were “clearly timed for President Biden’s return after his visit to South Korea and Japan,” Park Won-gon, a professor at Ewha University said, adding that Biden hadn’t even touched down in the US.