The South Korean military says North Korea launched three ballistic missiles in succession on Wednesday morning. The move came after US President Joe Biden concluded his visit to Seoul and Tokyo to strengthen trilateral ties.

South Korea's Joint Chiefs of Staff said the three missiles were fired at 6 a.m., 6:37 a.m. and 6:42 a.m. from the Sunan area near Pyongyang toward the Sea of Japan.

It says it is on heightened alert and is in close contact with US forces. South Korean President Yoon Suk-yeol has ordered a meeting of the National Security Council to be convened.

North Korea has frequently repeated launces of projectiles this year. This month alone, it launched a ballistic missile from near Sunan on May 4 and an apparent short-range ballistic missile from a submarine off the coast of the eastern city of Sinpho on May 7. It also fired three short-range ballistic missiles from near Sunan on May 12.

The latest launches come a day after Biden wrapped up his trip to Asia.

He first held talks with South Korea's new president in Seoul for the first time on Saturday. Biden affirmed America's "extended deterrence" commitment to South Korea through various means including nuclear weapons. The two leaders also agreed to discuss scaling up their joint military drills, which the North regards as a symbol of "hostile forces."

Biden then met with Japan's Prime Minister Kishida Fumio in Tokyo on Monday. They shared serious concerns about North Korea's nuclear and missile programs, and confirmed closer cooperation.

North Korea is currently trying to tackle what is believed to be a coronavirus outbreak by taking measures including lockdowns. It apparently aims to show that despite this situation, its nuclear and missile development remains unaffected.