North Korea launches ballistic missiles and warns of turning Pacific into 'firing range'

It comes just two days after Pyongyang fired an ICBM into the sea off Japan's west coast, prompting joint air exercises by the US and South Korea

A North Korean missile launch is shown on a news programme at the Seoul Railway Station in South Korea, on February 20. AP.

North Korea fired two ballistic missiles off its east coast, South Korea's military said on Monday, as the powerful sister of leader Kim Jong-un warned the isolated and nuclear-armed state could turn the Pacific into a "firing range".

The launches come just two days after North Korea fired an intercontinental ballistic missile into the sea off Japan's west coast, prompting joint air exercises by the US and South Korea on Sunday.

North Korea's state media confirmed it fired two projectiles from a rocket launcher, aiming at targets 395km and 337km away.

"The 600mm multiple rocket launcher mobilised in the firing … is a means of tactical nuclear weapon", capable of paralysing an enemy airfield, state news agency KCNA said.

Japan's Defence Ministry said the two missiles, fired about 7pm local time, reached a maximum altitude of about 100km and 50km, travelling about 350km to 400km before falling outside Japan's exclusive economic zone.

There were no reports of damage to aircraft or vessels.

The Japanese ministry said it would continue to gather and analyse information in close co-operation with the US.

"North Korea's series of actions, including its repeated ballistic missile launches, threaten the peace and security of Japan, the region and the international community," it said.

"Japan lodged a strong protest and forcefully condemned North Korea."

North Korean leader Kim's sister, Kim Yo-jong, warned against increased the presence of US strategic assets on the Korean Peninsula after the US held joint air exercises with South Korea, then Japan on Sunday.

"We are carefully examining the influence it would exert on the security of our state," Ms Kim said.

"The frequency of using the Pacific as our firing range depends upon the US forces' action character."

She denied experts' assessment of the North's missile capabilities after some said it took more than nine hours for the "sudden" missile launch to take place after an order from Mr Kim.

"We have possessed satisfactory technology and capability, and now will focus on increasing the quantity of their force," she said.

Monday's missile launch is the North's third major weapons test this year after Pyongyang threatened an "unprecedentedly persistent, strong" response as South Korea and the US geared up for their annual military exercises.