The yen surged to an 18-month high against the dollar Monday while the benchmark Nikkei index briefly dipped below 15,000 as fears mounted that ballooning subprime loan losses will trigger a recession in the U.S.

The yen touched the upper 109 range against the dollar Monday, the highest levels since May 2006. At 5 p.m., it traded at 110.31-33, up from 110.40-45 in New York and 112.65-68 in Tokyo at 5 p.m. Friday.

The 225-issue Nikkei stock average shed 386.33 points, or 2.48 percent, to close at 15,197.09, its lowest close since Aug. 7, 2006. The index briefly fell to 14,998.51, sinking below the 15,000 threshold for the first time since July 27, 2006. The Nikkei has lost nearly 1,700 points over the past seven trading days, its longest losing streak since early May 2005.