North Korea on Monday fired a long-range ballistic missile into the sea, Reuters and Yonhap news agencies reported, citing the South Korean military.
The long-range missile was fired just a few hours after Pyongyang had fired a short-range missile.
The consecutive missile launches followed a warning from the US and South Korea which threatened North Korea's end if it used nuclear weapons.
The test-fire was conducted from an area near the capital Pyongyang towards the sea off the North's east coast, South Korea's Joint Chiefs of Staff said.
Japan's coast guard said that the missile which appeared to be fired from North Korea fell into the sea west of Hokkaido about an hour after launch.
In a statement, South Korea's military said that the missile flew about 1,000 kilometers (620 miles) before landing in the sea. It said the missile was launched on an elevated angle, apparently to avoid neighboring countries.
Meanwhile, Japan's defense ministry said that the missile's flying range was large enough to cover the whole of US.
"The ICBM-class ballistic missile launched this time, if calculated based on the trajectory, depending on weight of warhead, could have a flying range of over 15,000 kilometers. In which case the whole of the US territory would be within the range," Japan's Parliamentary Vice-Minister of Defense Shingo Miyake said.
It is suspected that the international airport serving Pyongyang is where the missile assembly takes place in North Korea.
Mounting tensions in Korean peninsula
Monday's long-range missile was North Korea's second missile launch in less than 12 hours. It had fired a short-range ballistic missile on Sunday night, which flew about 570 km (350 miles) from an area near Pyongyang and then fell into the sea.
Following the missile launch on Sunday, Pyongyang had released a scathing statement against Washington alleging that the US was responsible for what it called a "preview of a nuclear war," including the arrival of a nuclear-powered submarine in South Korea on Sunday.
Pyongyang also criticized Washington's move to include nuclear contingencies in their joint drills, describing it as an open threat to potentially use nuclear weapons against the North. It vowed to prepare unspecified "offensive countermeasures."
mfi/wd (Reuters, AFP, AP, dpa)