Seoul: North Korea launched two ballistic missiles on Sunday morning, according to South Korea's military and Japan's coast guard.
"Our military has strengthened surveillance and vigilance while closely cooperating with the United States and maintaining a full readiness posture" South Korea's Joint Chiefs of Staff said.
Japan's defence ministry added that one of the missiles covered a distance of 500 km (310 miles) towards the Sea of Japan and flew at an altitude of 550 km.
"It threatens the peace and security of our country, this region, and the international community, and it is absolutely unacceptable," said the country's senior vice defence minister Toshiro Ino.
He added that the missiles appeared to have landed outside of Japan's exclusive economic zone (EEZ).
Advanced technologies in development
The missiles detected on Sunday appear to have been launched from the Tongchang-ri area, which is home to North Korea's Sohae Satellite Launching Ground.
The United Nations recently said Pyongyang's launches of satellite-carrying long-range rockets were a disguised test for intercontinental ballistic missile (ICBM) technology.
Sunday's missile launches also come just three days after North Korea said it tested a "high-thrust solid-fuel motor" for a new strategic weapon at the same facility.
All of North Korea's currently-known ICBMs use liquid fuel.
North Korea has ramped up missile tests this year amid large-scale American and South Korean joint training exercises off the Korean peninsula. Pyongyang views these drills as a rehearsal for invasion.
Some of North Korea's recently-tested missiles included mock nuclear warheads.
North Korean leader Kim Jong Un declared he wanted to build the world's most powerful nuclear force after the launch of the Hawsong-17 "monster" missile last month.