Japanese stocks fell as a slump in commodities heightened concern over slowing global economic growth amid weak U.S. earnings.

The Topix index declined 0.3 percent to 1,660.07 as of 9:01 a.m. in Tokyo, with all but eight of its 33 industry groups falling. The measure is headed for an 0.2 percent loss this week. The Nikkei 225 Stock Average dropped 0.4 percent to 20,601.30, tracking losses in U.S. shares, which were dragged lower by slumping energy prices and poor earnings results.

Oil relapsed into a bear market as resilient U.S. output, rising OPEC supply and threats to Chinese demand deepen a global supply glut. After its nuclear accord with world powers, Iran will focus on regaining the share of the oil market market it lost due to sanctions, regardless of the impact on prices, a government official said on Monday.

Source : Bloomberg