TOKYO, Feb 18 (Reuters) - Japan's Nikkei share average soared to a 2-1/2-week high on Tuesday, led by the banking sector after the Bank Of Japan said it would extend loan facilities by a year at its policy meeting. As widely expected, the BOJ kept monetary policy steady and maintained its upbeat assessment on the economy. It also decided to extend three special loan facilities by a year from their scheduled expiry at the end of March. The Nikkei ended 3.1 percent higher at 14,843.24, the highest close since Jan. 31. The Topix gained 2.7 percent to 1,224.00. The JPX-Nikkei Index 400, an index launched this year comprised of firms with high return on equity and strong corporate governance, advanced 2.7 percent to 11,067.44.