The country's three largest maritime transport companies reported a unconsolidated sales increase for the first half of fiscal 1998 due to the weakened yen, the carriers announced Friday.

For the April-September period, Nippon Yusen K.K. posted 341.5 billion yen in sales, up 9 percent from the same period of the previous year. The carrier posted 14.9 billion yen in operating profit, up 22.9 percent from the year before, with a net profit of 2.1 billion yen.

Mitsui O.S.K. Lines Ltd. sales also grew 7.8 percent to 305.2 billion yen from the previous year. The carrier posted 11.9 billion yen in operating profit, up 52.8 percent from the year before, while its net profit also rose 51.1 percent to 4.4 billion yen.

In the midterm earnings reports, both Nippon Yusen and Mitsui O.S.K. recorded their highest sales for the first half of a business year. Kawasaki Kisen Kaisha Ltd. posted 207.1 billion yen in sales, up 10.2 percent from the year before, though its operating profit declined 12 percent to 8.6 billion yen. Its net profit dropped 2 percent to 1.5 billion yen.