North Korea fired a barrage of short-range ballistic missiles into the sea on Tuesday, its neighbours said, as it continued its weapons demonstrations hours before the US presidential election.

Japanese Defence Minister Gen Nakatani said at least seven North Korean missiles flew as far as 400 kilometres with a maximum altitude of 100 kilometres.

He said they landed in the waters between the Korean Peninsula and Japan.

“North Korea’s actions, including a series of repeated missile launches, threaten the peace and safety of Japan, the region and the international community,” Nakatani said.

South Korea's military also detected several missile launches by North Korea and subsequently boosted its surveillance posture.

The North Korean missiles could be used to target key facilities in South Korea, including US military bases there.

The launches 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 on Sunday in a show of force.

That drew condemnation from Kim’s powerful sister Kim Yo-jong, who on Tuesday accused North Korea’s rivals of raising tensions with “aggressive and adventuristic military threats.”

South Korean officials have said that North Korea was likely to dial up its military displays around the US presidential election 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.

Outside officials and analysts say North Korea eventually hopes to use an expanded nuclear arsenal as leverage to win concessions such as sanctions relief after a new US president is elected. (AP)