TOKYO, Feb. 9 (Xinhua) -- Tokyo stocks extended losses Friday morning as investor concerns were reignited by another heavy sell-off on Wall Street overnight after the 10-year U.S. Treasury yield spiked.

The 225-issue Nikkei Stock Average dropped 705.10 points, or 3.22 percent, from Thursday to 21,185.76.

The broader Topix index of all First Section issues on the Tokyo Stock Exchange, meanwhile, lost 50.17 points, or 2.84 percent, to 1,715.52.

Nonferrous metal, machinery and mining issues comprised the biggest decliners by the morning break as all industry categories on the main section retreated.