SEOUL — North Korea fired three ballistic missiles off its east coast on Wednesday, Seoul’s military said, just hours after US President Joseph R. Biden left the region following a trip in which he agreed to boost measures to deter the nuclear-armed state.

South Korea’s Joint Chiefs of Staff said the three ballistic missile launches were fired in the space of less than an hour from the Sunan area of the North’s capital Pyongyang.

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

US and South Korean officials had recently warned that North Korea appeared ready for another weapon test, possibly during Mr. Biden’s visit, which was his first trip to Asia as president.

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

Japan reported at least two launches, but acknowledged that there may have been more. One of the missiles flew a distance of about 750 km (465 miles) to a maximum altitude of 50 km and appeared to be capable of shifting its trajectory in flight, Japan’s defense minister said. Another missile flew about 300 km and reached a maximum altitude of 550 km, he said.

Japanese broadcaster NHK said the missiles appeared to have fallen outside Japan’s exclusive economic zone (EEZ).

The US military’s Indo-Pacific Command said it was aware of “multiple” launches. They highlighted the “destabilizing impact of the DPRK’s illicit weapons program” but did not pose an immediate threat, it said in a statement, using the initials of North Korea’s official name.

In Seoul at the weekend, Mr. Biden and his South Korean counterpart Yoon Suk-yeol agreed to hold bigger military drills and deploy more US strategic assets if necessary to deter North Korea’s intensifying weapon tests.

But they also offered to send coronavirus disease 2019 (COVID-19) vaccines to North Korea as the isolated country battles its first confirmed outbreak, and called on Pyongyang to return to diplomacy.

There had been no response from Pyongyang to the diplomatic overtures or offers of aid, Mr. Biden said at the time.

The waning hours of Mr. Biden’s visit to the region also saw Russian and Chinese bombers flying joint patrols near Japanese and South Korea air defense zones on Tuesday in a pointed farewell. — Reuters