The projectile is believed to have fallen outside Japan's exclusive economic zone, according to public broadcaster NHK citing government officials.

South Korea's military also said Pyongyang fired a ballistic missile towards the Sea of Japan, Kyodo news agency reported.

Pyongyang routinely conducts weapons tests, and the incident comes days after leader Kim Jong Un personally oversaw the firing of the country's newest intercontinental ballistic missile, the solid-fuel Hwasong-18.

Relations between the two Koreas are currently at one of their lowest historical points, as diplomacy between Pyongyang and Seoul has stalled and Kim has called for ramping up weapons development, including tactical nukes.

In response, Seoul and Washington have staged joint military exercises with advanced stealth jets and US strategic assets.

The launch also comes ahead of celebrations in North Korea this week marking the 70th anniversary of the end of the Korean War.

A Chinese delegation will travel to the North in what is the first known visit by a foreign delegation since the start of the Covid-19 pandemic, the state-run Korean Central News Agency reported.