TOKYO, Dec. 19 (Xinhua) -- Tokyo stocks opened lower Wednesday as concerns over a U.S. government shutdown, a slump in oil prices and concerns that the U.S. Federal Reserve may go too far with its rate-hiking policy led to investor consternation.

As of 9:15 a.m., the 225-issue Nikkei Stock Average dropped 166.53 points, or 0.79 percent, from Tuesday to 20,948.92.

The broader Topix index of all First Section issues on the Tokyo Stock Exchange, meanwhile, lost 8.90 points, or 0.57 percent, at 1,553.61.

Mining, oil and gas product, and marine transportation-linked issues comprised those that declined the most in the opening minutes after the morning bell.