North Korea today fired at least one ballistic missile toward its eastern sea, according to the South Korean military, as the country continued its weapons demonstrations hours before the US presidential elections.

South Korea's Joint Chiefs of Staff didn't immediately say what type of missile it was or how far it flew. Japan's Defence Ministry said the missile was believed to have already landed at sea.

The launch came days after North Korean leader Kim Jong Un supervised a flight test of the country's newest intercontinental ballistic missile designed to reach the US mainland.

In response to that launch, the United States flew a long-range B-1B bomber in a trilateral drill with South Korea and Japan in a show of force.

That drew condemnation from Kim's powerful sister, who accused the North's rivals of raising tensions with "aggressive and adventuristic military threats".

North Korean state media claimed last week that the Hwasong-19 it tested on October 31 was "the world's strongest" ICBM, but experts say the solid-fuel missile was too big to be useful in a war situation.

Experts say the North has yet to acquire some critical technologies to build a functioning ICBM, such as ensuring that the warhead survives the harsh conditions of atmospheric re-entry.

The latest launches came after South Korean officials said the North was likely to dial up its military displays around the US presidential elections to command the attention of Washington.

South Korea's military intelligence agency said last week that North Korea has also likely completed preparations for its seventh nuclear test.

Tensions between the Koreas are at their highest point in years as Kim has repeatedly flaunted his expanding nuclear weapons and missile programs, while reportedly providing Russia with munitions and troops to support President Vladimir Putin's war in Ukraine.

After a meeting in Seoul yesterday, South Korean Foreign Minister Cho Tae-yul and EU foreign policy chief Josep Borrell expressed "deep concern" over the possibility that Russia transfers any nuclear or ballistic missile-related technology to the North in exchange for its arms and military personnel.

Such transfers would "jeopardise the international non-proliferation efforts and threaten peace and stability on the Korean Peninsula and across the globe", they said, while calling on North Korea and Russia to immediately withdraw the troops from Russia.

In response to North Korea's growing nuclear threats, South Korea, the United States and Japan have been expanding their combined military exercises and updating their nuclear deterrence plans built around US strategic assets.