Defending women's champions China were upset in straight sets by Turkey in their Olympic Pool B opener on Sunday, going down 25-21 25-14 25-14 at the Ariake Arena.
China, who have won six Olympic medals in women's volleyball including three gold, were overpowered by the Turks for whom Ebrar Karakurt led the way with 18 points while three others finished in double figures.
Earlier, the top-ranked U.S. women rode on Olympic debutants Jordan Thompson's 20 points and Michelle Bartsch-Hackley's 13 to ease past Argentina 25-20 25-19 25-20 at Tokyo's Ariake Arena.
Serbia and Italy also sealed straight-sets victories over the Dominican Republic and the Russian Olympic Committee team respectively.
(Reporting by Rohith Nair in Bengaluru, editing by Ed Osmond)