The nation's three largest securities companies all realized net losses for the first half of fiscal 1998 on an unconsolidated basis, they said in releasing midterm earnings reports Thursday.Nomura Securities Co., Daiwa Securities Co. and Nikko Securities Co., which all released results for the April-September period, faced current sluggish stock trading at home as well as a tumultuous situation on international financial markets.In terms of net profit, all three brokerages fell into the red. Nomura, Japan's leading brokerage, registered 8.35 billion yen in losses, while Daiwa posted losses of 44.68 billion yen and Nikko lost 31.52 billion yen, the results show.For midterm fiscal 1997, Nomura secured 41.52 billion yen, Daiwa posted 13.53 billion yen and Nikko showed 4.3 billion yen in net profit.Regarding pretax profit, Nomura managed to secure 21.88 billion yen in profits for the latest midterm, although the figure was down 55.6 percent from midterm 1997, during which it logged profits of 49.3 billion yen.Officials of the brokerages blamed Japan's bearish stock market, volatile overseas financial markets and sharp falls in brokerage commission revenues since April's liberalization of commissions on large-lot orders.Nomura officials said the brokerage was hit hard by overseas factors such as the Russian financial crisis. Nomura's U.S. and British subsidiaries incurred losses totaling $600 million in investment in Russian government bonds and in currency swaps as of the end of September, they said.In response, the firm will soon inject $1.2 billion into Nomura Holding America Inc., Nomura's U.S. holding company, which suffered a $1.1 billion appraisal loss on real estate-related securities, they said.Daiwa suffered an appraisal loss of 34.8 billion yen on domestic stockholdings. It also lost 14 billion yen in investment in emerging markets in Asia, while Nikko posted a domestic portfolio loss of 250 billion yen. Daiwa said it will implement a 20 percent cut in operational costs, worth 40 billion yen, by consolidating its branch offices and reducing its workforce, while Nikko also said it would introduce similar measures.