Pyongyang, North Korea - North Korea fired a ballistic missile Friday, Seoul's military said, around a week after US President Donald Trump approved South Korea's plan to build a nuclear-powered submarine.

Analysts have said Seoul's plan to construct one of the atomic-driven vessels – approved by Trump last week – would likely draw an aggressive response from Pyongyang.

South Korea's Joint Chiefs of Staff said North Korea fired an unidentified ballistic missile towards the East Sea, referring to the body of water also known as the Sea of Japan.

The missile landed in the sea outside Japan's economic waters and no damage or injuries had been reported, said Japanese Prime Minister Sanae Takaichi.

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But the Kremlin defended North Korea's latest launch, saying Pyongyang – a key ally for Russia during its Ukraine campaign – had the "legitimate right" to do so.

"We are respectful of the legitimate right of our friends in the DPRK to ensure their security and take measures for it," Kremlin spokesperson Dmitry Peskov told reporters.

Japan, meanwhile, said North Korea's ballistic missile launches have been "absolutely unforgivable."

As "evidenced" by North Korea's actions, "it's never too early to accelerate efforts to revamp our defense capabilities," Defence Minister Shinjiro Koizumi said.

"We will consider what steps are needed to protect our nation's... peace and the lives of our people, without ruling out any options."

The missile launched around noon local time from an area north of Pyongyang and flew around 435 miles, South Korea's military said.

North Korea has significantly increased missile testing in recent years, which analysts say is aimed at improving precision strike capabilities, challenging the US as well as South Korea, and testing weapons before potentially exporting them to Russia.