Pyongyang - North Korea reportedly fired a ballistic missile early on Sunday in what would be its first such test of the year and an implicit challenge to US President Donald Trump, who stood with the Japanese leader as Shinzo Abe called the move "absolutely intolerable".Details of the launch, including the type of missile, were scant.There was no immediate confirmation from the North, which had recently warned it is ready to test its first intercontinental ballistic missile. The reports come as Trump was hosting Abe and just days before the North is to mark the birthday of leader Kim Jong Un's late father, Kim Jong Il.Appearing with Trump at a news conference at the president's south Florida estate, Abe condemned the missile launch as "absolutely intolerable". Trump followed Abe with even fewer words, saying in part: "I just want everybody to understand and fully know that the United States of America stands behind Japan, its great ally, 100 percent."Abe read a brief statement in which he called on the North to comply fully with relevant UN Security Council resolutions. He said Trump has assured him of US support and that Trump's presence showed the president's determination and commitment.Previous testsSouth Korea's Joint Chiefs of Staff said in a statement the missile was fired from around Banghyon, North Pyongan Province, which is where South Korean officials have said the North test launched its powerful midrange Musudan missile on October 15 and 20.The military in Seoul said that the missile flew about 500km. But Yonhap reported that while determinations are still being made, it was not believed to be an ICBM.The missile is believed to have splashed down into the sea between the Korean Peninsula and Japan. Japan's Chief Cabinet Secretary Yoshihide Suga told reporters the missile did not hit Japanese territorial seas. The North conducted two nuclear tests and a slew of rocket launches last year in continued efforts to expand its nuclear weapons and missile programmes. Kim Jong Un said in his New Year's address that the country has reached the final stages of readiness to test an ICBM, which would be a major step forward in its efforts to build a credible nuclear threat to the United States.Though Pyongyang has been relatively quiet about the transfer of power to the Trump administration, its state media has repeatedly called for Washington to abandon its "hostile policy" and vowed to continue its nuclear and missile development programmes until the US changes its diplomatic approach.Space launchesJust days ago, it also reaffirmed its plan to conduct more space launches, which it staunchly defends but which have been criticised because they involve dual use technology that can be transferred to improve missiles.Kim Dong-yeop, an analyst at the Institute for Far Eastern Studies in Seoul, speculated the missile could be a Musudan or a similar rocket designed to test engines for an intercontinental ballistic missile that could hit the US mainland. Analysts are divided, however, over how close the North is to having a reliable long-range rocket that could be coupled with a nuclear warhead capable to striking US targets.South Korea's Acting President and Prime Minister Hwang Kyo-ahn said that his country will punish North Korea for the missile launch. According to the Foreign Ministry, South Korea will continue to work with allies including the United States, Japan and the European Union to ensure a thorough implementation of sanctions against the North and make the country realise that it will "never be able to survive" without discarding all of its nuclear and missile programmes.