Japan's benchmark Nikkei stock index closed at more than a 21-year high Thursday as investor sentiment was bolstered by optimism for growth in the U.S. economy, a possible rate hike by the U.S. Federal Reserve and tax reforms.

The 225-issue Nikkei Stock Average gained 119.04 points, or 0.53 percent, from Wednesday to close the day at 22,539.12, marking its highest close since June 1996.

The broader Topix index of all First Section issues on the Tokyo Stock Exchange, meanwhile, gained 7.37 points, or 0.41 percent, to finish at 1,794.08.

Mining, transportation equipment and nonferrous metal-oriented stocks comprised those that gained the most by the close of play.