Japan says tests proof of intensifying threats; South Korea's Foreign Ministry warns North Korea may face even stronger sanctions.
North Korea launched what appeared to be an intermediate-range missile on Wednesday to a high altitude in the direction of Japan before it plunged into the sea, military officials said, in a move which appeared to mark a technological advance for the isolated state after several failed tests.
The launch came about two hours after a similar test failed, South Korea's military said, with the missile covering 400 kilometres (250 miles) – more than half the distance to the southwest coast of Japan's main island of Honshu.
Both tests were believed to be of the intermediate-range Musudan missile, capable of reaching US bases as far away as Guam and any part of Japan. However, BBC reported that North American Defense Command tracked the missiles and determined they did not pose a threat to North American territories.
The launches and earlier nuclear tests show continued defiance of international warnings and a series of UN Security Council resolutions and sanctions, which North Korea rejects as an infringement of its sovereignty. Existing UN Security Council measures ban North Korea from any use of ballistic missile technology.
Japanese Defence Minister Gen Nakatani said the second missile reached an altitude of 1,000 kilometres (620 miles) and a range of 400 km, indicating North Korea had made progress.
"We don't know whether it counts as a success, but North Korea has shown some capability with IRBMs [intermediate range ballistic missiles]," he told reporters in Tokyo. "The threat to Japan is intensifying."
The first test took place shortly before 6am (2100 GMT Tuesday) and was deemed to have failed after the rocket reportedly flew around 150 km (90 miles) over the East Sea (Sea of Japan).
"South Korea and the United States are conducting further analysis," the South Korean Defence Ministry said in a statement that stopped short of labelling the second test a success or failure.
A successful test would mark a major step forward for a weapons programme that ultimately aspires to develop a proven nuclear strike capability against the US mainland and North Korea's neighbours.
US State Department spokesman John Kirby said the latest launches would only increase global efforts to counter North Korea's illicit weapons programme.
"We intend to raise our concerns at the UN to bolster international resolve in holding (North Korea) accountable for these provocative actions," Kirby said in a statement.
Japanese broadcaster NHK quoted Prime Minister Shinzo Abe as saying such tests "cannot be tolerated."
Nakatani said further provocative action from Pyongyang could not be ruled out, and suggested the twin launches could have been timed to coincide with the 66th anniversary of the start of the Korean War in 1950.
The South Korea and North Korea technically remain in a state of war after the 1950-53 Korean War ended in an armistice, not a peace treaty.
South Korea's foreign ministry warned that North Korea would face even stronger sanctions and said the tests underlined "the hypocrisy and deceptiveness" of Pyongyang's recent offers of military talks with Seoul.
First unveiled as an indigenous missile at a military parade in Pyongyang in October 2010, the Musudan has a theoretical range of anywhere between 2,500 and 4,000 km.
The lower end of the estimate covers the whole of South Korea and Japan, while the upper range would include US military bases in Guam.
Four Musudan missiles tested earlier this year all either exploded on the mobile launch pad or shortly after take-off.
The three failed launches in April were seen as an embarrassment for North Korea's leadership, coming ahead of a rare ruling party congress that was meant to celebrate the country's achievements.
Another attempt in May was also deemed to have failed.
A North Korean breakthrough?
South Korea's Yonhap news agency quoted an unidentified high-ranking government official as saying the second test on Wednesday demonstrated an obvious "improvement in capacity and technology."
The official said the missile appeared to have been fired on an unusually high trajectory to limit its range.
A Japanese Defence Ministry spokesman said it "exhibited a certain functionality."
Military tensions between North and South Korea remain heightened following Pyongyang's fourth nuclear test in January. A month later, a long-range rocket launch led the UN Security Council, backed by China, to impose its toughest sanctions to date on North Korea.
In recent months, North Korea has claimed a series of technical breakthroughs in developing an intercontinental ballistic missile (ICBM) capable of delivering a nuclear warhead to targets across the United States.
North Korea is believed to have up to 30 Musudan missiles, according to South Korean media, which officials said were first deployed around 2007. North Korea did not attempt to test-fire them until April.
North Korea has displayed an ICBM, the KN-08, during military parades, but it has never been tested.
Melissa Hanham, an expert on North Korea's weapons of mass destruction programme at Middlebury Institute of International Studies in California, said Wednesday's launches represented a worrying step forward.
"I don't know if it's a success, but it is definitely progress. Testing is iterative and they are learning from each flight," Hanham told AFP.
"Policymakers need to focus on a testing ban to prevent this from becoming a working missile."
In Seoul, a national security meeting will be convened on Wednesday to discuss the latest missile launches, South Korea's presidential office said.