North Korea fired a suspected long-range missile designed to strike the mainland US on Friday, its neighbours said, a day after the North resumed its testing activities in an apparent protest over US moves to solidify its alliances with South Korea and Japan.

The South's Joint Chiefs of Staff said in a statement that it detected a ballistic missile launch off the North's eastern coast on Friday morning. It later said the missile launched is likely an intercontinental ballistic missile.

The Japanese Defence Ministry also said in a statement that North Korea fired an ICBM-class ballistic missile from its western coastal area that flew toward its eastern waters across the country. It said the missile, launched at around 10:14 am (0114 GMT) was still in flight and may land inside of the Japanese Exclusive Economic Zone.

If confirmed, it would be North Korea's first ICBM launch in about two weeks. Outside experts said that an ICBM launched by North Korea on November 3 failed to fly its intended flight.

The November 3 test was believed to have involved a new type of developmental ICBM. North Korea has two other types of ICBM -- Hwasong-14 and Hwasong-15 -- and their test-launches in 2017 proved that they could potentially reach parts of the US homeland.

South Korea's presidential office said it convened an emergency security meeting to discuss the North Korean launch.

"North Korea has been repeatedly firing missiles this year at an unprecedented frequency and is significantly escalating tensions on the Korean peninsula," Japanese Defence Minister Yasukazu Hamad told reporters.

The launch is the latest in a slew of missile tests by North Korea in recent weeks. But the country had halted weapons launches for about a week before it fired a short-range ballistic missile on Thursday.

Before Thursday's launch, the North's foreign minister, Choe Son Hui, threatened to launch "fiercer" military responses to the US bolstering its security commitment to its allies South Korea and Japan.

Choe was referring to US President Joe Biden's recent trilateral summit with his South Korean and Japanese counterparts on the sidelines of a regional gathering in Cambodia. In their joint statement, the three leaders strongly condemned North Korea's recent missile tests and agreed to work together to strengthen deterrence. Biden reaffirmed the US commitment to defend South Korea and Japan with a full range of capabilities, including its nuclear arms.

Choe did not say what steps North Korea could take but said that "the US will be well aware that it is gambling, for which it will certainly regret".