Despite sluggishness in the domestic auto market, the nation's five major automakers are all enjoying higher sales for the 1997 business year, according to half-year financial results announced Friday.

All automakers except Mitsubishi Motors Corp. posted pretax profits, thanks to the weak yen and strong exports, particularly to the United States and Europe.

Due to lackluster domestic sales, most revised downward their sales forecasts for the full year. However, the companies said they still expect to have relatively high pretax profit levels thanks to steady growth in exports and sales from new models introduced before the Tokyo Motor Show in October.

Toyota Motor Corp.'s net sales declined 7 percent partly because of a change in accounting methods. Calculations under its old system would have shown a rise in sales.

Mazda Motor Corp., helped by a combination of factors including good exchange rates, improved sales, and active cost-cutting efforts, reported a pretax profit of 5.19 billion yen for the April-September period, up 149.7 percent from the same period the previous year, said Gary Hexter, Mazda's senior managing director. Mazda expanded net sales 11.4 percent to 746.22 billion yen and managed to post a 7.14 billion yen midterm operating profit -- its first in five years.

The five automakers said Thailand's economic crisis had only a relatively minor impact on half-year profits, but that their business would be severely affected in the latter half of the year.