The United States has held joint air exercises bilaterally with South Korea and Japan involving strategic bombers a day after North Korea fired a long-range ballistic missile in a “sudden launching drill”.

South Korea’s Joint Chiefs of Staff said the exercise, in which South Korea and US jet fighters escorted American B-1B bombers, demonstrated the allies’ “overwhelming” defence capabilities and readiness posture.

“[The exercise] strengthened the combined operation capability and affirmed the United States’ iron-clad commitment to the defence of the Korean Peninsula and the implementation of extended deterrence,” South Korea’s military said in a statement on Sunday.

Japan flew F-15s over the Sea of Japan with the US Armed Forces’ B-1 bombers and F-16s in tactical exercises, Japan’s Defence Ministry said in a statement, calling the security environment “increasingly severe” after the latest North Korea missile landed within its Exclusive Economic Zone.

“This bilateral exercise reaffirms the strong will between Japan and the United States to respond to any situation, the readiness of [Japan’s Self Defence Forces] and US Armed Forces, and further strengthens the deterrence and response capabilities of the Japan-US Alliance,” the ministry said.

The air drills come a day after North Korea launched a long-range ballistic missile into the sea off Japan’s west coast, following a warning of a strong response to upcoming military drills by South Korea and the US.

North Korea’s state media KCNA said the country conducted a “sudden launching drill” on Saturday in an “actual proof” of its efforts to turn the “capacity of fatal nuclear counterattack on the hostile forces into an irresistible one”.

Leader Kim Jong-un’s sister, Kim Yo Jong, issued yet another warning and accused the US of trying to turn the UN Security Council into what she called a “tool for its heinous hostile policy” toward Pyongyang.

“I warn that we will watch every movement of the enemy and take corresponding and very powerful and overwhelming counteraction against its every move hostile to us,” she said in a statement.

Saturday’s missile launch, North Korea’s first since January 1, came after Pyongyang threatened on Friday an “unprecedentedly persistent, strong” response as South Korea and the US geared up for their annual military exercises as part of efforts to fend off the growing nuclear and missile threat that the North poses.

North Korea’s state news agency said its missile had flown for one hour, six minutes and 55 seconds, as high as 5768 kilometres, before accurately hitting a pre-set area 989 kilometres away in open waters.

It first test-fired a Hwasong-15 in 2017.

-Reuters