North Korea has fired three missiles, including one thought to be an intercontinental ballistic missile (ICBM), after US President Joe Biden left Asia following a trip in which he agreed to new measures to deter the nuclear-armed state.

South Korea's Joint Chiefs of Staff (JCS) said the three missiles were fired in less than an hour from the Sunan area of the North's capital, Pyongyang, where its international airport has become a hub of missile tests.

The first missile launched this morning appeared to be an ICBM, while a second unidentified missile appears to have failed mid-flight, the JCS said. The third missile was a short-range ballistic missile (SRBM), it said.

In response, the United States and South Korea held combined live-fire drills, including surface-to-surface missile tests involving the Army Tactical Missile System (ATACMS) of the US and the South's Hyunmoo-2 SRBM, both militaries said.

"Our military's show of force was intended to highlight our resolve to firmly respond to any North Korean provocations, including an ICBM launch, and our overwhelming capability and readiness to conduct a surgical strike on the origin of the provocation," the JCS said in a statement.

US President Joe Biden and South Korean President Yoon Suk-yeol at the National Museum of Korea

North Korea has conducted a flurry of missile launches this year, from hypersonic weapons to test firing its largest ICBMs for the first time in nearly five years. It also appears to be preparing for what would be its first nuclear test since 2017.

US and South Korean officials had recently warned that North Korea appeared ready for another weapons test, possibly during Mr Biden's visit, which was his first trip to Asia as president and included a summit with South Korean President Yoon Suk-yeol in Seoul.

Mr Yoon, who took office on 10 May, convened his first meeting of the national security council, which strongly condemned the latest launch as a "grave provocation", especially as it came before Mr Biden returned home.

Mr Yoon ordered the aides to strengthen the US extended deterrence and combined defence posture as agreed with Mr Biden, his office said.

"North Korea's continued provocations will only result in even stronger, faster South Korea-US deterrence, and bring deeper isolation upon itself," Mr Yoon's government said in a separate statement.

A White House official said that Mr Biden, who departed Japan yesterday evening, had been briefed on the launches and would continue to receive updates.