North Korea has ordered its people to raise the country's flag and tune in for a message on state-run television Sunday amid apparent indications that the communist nation may have fueled a long-range missile in preparations for a launch, news reports said. North Korea is believed to have begun filling a ballistic missile with fuel, Japan's largest daily Yomiuri reported Sunday, citing unnamed US government officials who conveyed information Saturday to the Japanese government through unofficial channels. The US and Japan have confirmed that assembly of what is believed to be a Taepodong-2 missile has been completed with two stages at the launch site, based on photos from satellites, the paper said. The Taepodong-2 missile is believed to be the North's most advanced model with the capability to reach the United States with a light payload. South Korea's Yonhap news agency, citing diplomatic sources in Washington, also reported there was a possibility the missile may have already been fueled, with satellite photos showing tens of fuel tanks at the launch site. "But, we cannot say this for sure," one unidentified source was quoted as saying by Yonhap, regarding the fueling of the missile. Other countries have urged North Korea to halt preparations for a test-launch of a long-range missile, after news reports said the North had loaded booster rockets onto a launch pad and could test-fire the missile as early as Sunday. Japan's Foreign Minister Taro Aso said Tokyo would seek an immediate meeting of the United Nations Security Council if North Korea fires the missile, and that a consideration of sanctions was "inevitable," Kyodo News agency reported Sunday. Kyodo earlier said Tokyo and Washington had agreed to ask the Security Council to get involved if the North goes ahead with the launch, citing unnamed government officials from several countries in a dispatch from New York. Washington holds one of the five permanent seats on the Security Council. The moves also come amid an extended impasse at international talks on the North's nuclear weapons program, which haven't met since November. The North has claimed it has a nuclear weapon, but it isn't believed to have a design that would be small and light enough to place on top of a missile. One diplomat in Washington told Yonhap that the US will employ "all measures" in case of a test fire, but indicated it will closely monitor the missile's track before taking any immediate action. Pyongyang stunned Tokyo and other nations when it test-fired a ballistic missile over northern Japan in 1998. It claimed then it was seeking to place a satellite in orbit. The communist nation has been under a self-imposed moratorium on long-range missile tests since 1999. However, it has since test-fired short-range missiles many times, including two in March.