Japan's defense agency has retracted an earlier statement saying that North Korea had fired a ground-to-ship missile, saying it was still trying to confirm its information. The retraction came after South Korea said there was no evidence of a North Korean missile launch.

Japanese officials scrambled Tuesday to correct an earlier statement on a North Korean missile launch, saying that they were unsure if the launch had occurred and were still trying confirm it.

Earlier in the day, several Japanese officials, including the head of the navy and the transport minister, told reporters that the North had fired a short-range missile.

Pyongyang tested two short-range missiles in the last two months.

At first, South Korea described the launch as routine, but within hours, Seoul said it had been unable to confirm that it had occurred. Shortly thereafter, Japan said the same, but said it would continue to seek more information. Tokyo has not disclosed the source of its information for security reasons.

The confusion comes amid heightened concerns over North Korea's nuclear ambitions and fears that Pyongyang might test a longer-range missile in the next few weeks, while Washington is preoccupied with the U.S.-led war in Iraq.

Tensions continue to simmer on the Korean Peninsula. They first flared in October, when the United States said North Korea admitted to running an illegal nuclear weapons program. The United States cut off fuel aid to Pyongyang. Since then, North Korea has withdrawn from a global nuclear non-proliferation treaty and engaged in several provocative acts.

North Korea recently pledged to strengthen its military. North Korea has repeatedly accused the United States of planning to attack it. It said military exercises between South Korean and U.S. troops now under way in the South are a warm-up for an invasion.

The United States denies it plans to invade and has said it wants to persuade North Korea to abandon its nuclear efforts through diplomacy.

However, Washington has moved additional jet bombers to Asia, as a warning to North Korea to not become aggressive. Also, on Tuesday, U.S. military officials said that several stealth fighter jets, F-15 fighters and an extra army contingent will remain in South Korea for a few weeks after the exercises with the South end, as an additional deterrence.