TOKYO, July 8 - Japan braced Tuesday for one of its worst storms in years as typhoon Neoguri barrelled towards the southern Okinawa island chain, with the national weather agency issuing its highest alert and nearly half-a-million people urged to take shelter. The top-level warning means a threat to life, as well as the risk of storm surges, landslides and massive damage from the typhoon packing gusts of up to 250 kilometres (155 miles) per hour. The Japan Meteorological Agency late Monday issued the alert for Okinawa's main island, home to around 1.2 million people, as well as the outlying Miyako islands. Waves could reach as high as 14 metres (45 feet), a weather agency official said, as schools across the sprawling archipelago south of Japan's main islands were closed while air and sea traffic services ground to a halt. About 6,500 Okinawan households had no power early Tuesday. The storm comes less than a year after typhoon Haiyan, packing the strongest winds ever recorded on land, killed or left missing more than 7,300 people as it tore across the central Philippines in November. "There are fears about violent winds, high waves and tides and torrential rain that we have never experienced before," Satoshi Ebihara, the Japanese weather agency's chief forecaster, told an evening news conference Monday. "We are in an abnormal situation where serious danger is imminent," he said, advising Okinawans to stay in secure buildings or seek out a safer location if they fear their homes could not withstand the powerful storm.

'Deadly' projectiles The Kadena Air Force Base, the biggest US Air Force base in the Pacific, located on Okinawa's main island, has evacuated some of its aircraft as officers stressed that Neoguri may be deadly. Authorities have now urged about 480,000 people across Okinawa to take shelter in their homes or evacuate to facilities such as community centres and town halls. "The rain is becoming heavier as the typhoon approaches," a municipal official of Nanjo told AFP by telephone. "We have urged residents to evacuate when they see any danger." The typhoon, which has been downgraded from super typhoon status, was about 90 kilometres (56 miles) northeast of Miyako Island as of 10:00am (0100 GMT), according to the weather agency. The storm was moving north at about 20 kilometres (12.4 miles) per hour, it said. The storm could reach the southern main island of Kyushu as early as Wednesday, with the weather agency warning that the amount of rainfall by Thursday could reach as much as 400 millimetres (16 inches), posing a serious risk of landslides and flooding. Kyushu -- next to the main island of Honshu, where major cities including Tokyo and Osaka are located -- was already seeing heavy rain. US officials at Kadena Air Force Base, home to thousands of American service people and their families, has warned residents to take serious precautions. "I can't stress enough how dangerous this typhoon may be when it hits Okinawa," Commander James Hecker of the 18th Wing stationed in Kadena said in a statement posted online. "This is the most powerful typhoon forecast to hit the island in 15 years. "So be prepared! Tie down your outdoor items and work with your neighbours to help them." He added: "During the typhoon, do not go outside... anything not tied down, even small items, could become deadly projectiles."