Major Japanese firms posted robust year-on-year profit rises in the April-June quarter due to the yen's decline, an oil price plunge and fading adverse effects of the consumption tax hike in April 2014, according to data compiled by a major brokerage.

The combined pretax profits rose 37 percent for 587 companies that reported April-June earnings by last Friday, among 1,268 non-financial firms that are listed on the Tokyo Stock Exchange's first section and close annual books in March, a tally by SMBC Nikko Securities Inc. found.

The companies' combined pretax profit forecasts for fiscal 2015 to next March 31 represent a 14 percent increase from the previous year.

Chemical companies took advantage of the oil price plunge to boost their earnings in the quarter, while air carriers and retailers benefited from a massive number of foreign tourists who were prompted by the weakening yen to visit Japan.

Transportation and electronics companies increased their combined pretax profits by some 20 percent as exports profitability improved due to a tailwind of the weaker yen.

But machinery-makers expect that pretax profit growth for fiscal 2015 could be limited to less than 2 percent due to a demand decline in China where economic growth is decelerating.

Full-year pretax profits are expected to decline in seven of the 29 business categories.