TOKYO, Jan. 6 (Xinhua) -- Tokyo stocks opened sharply lower on Monday, the first trading day of 2020, as the market mood was dented by U.S. shares tracking lower late last week amid rising tensions between the United States and Iran.

As of 9:15 a.m., the 225-issue Nikkei Stock Average dropped 431.75 points, or 1.83 percent, from Dec. 30 to 23,224.87.

The broader Topix index of all First Section issues on the Tokyo Stock Exchange, meanwhile, lost 25.79 points, or 1.50 percent, at 1,695.57.

Marine transportation, securities house, and pulp and paper-oriented issues comprised those that declined the most in the opening minutes after the morning bell.

Tokyo markets were closed from Tuesday to Friday for the New Year holidays.