Refiners including JX Holdings Inc., Japan's largest, have cut capacity by a combined 10 percent to meet government rules meant to compel them to upgrade facilities or reduce output.

Total Japanese refining capacity as of Tuesday was about 3.95 million barrels a day, according to data compiled by Bloomberg.

That compares with 4.38 million barrels a day as of March 22, according to the latest available weekly data compiled by the Petroleum Association of Japan.

The Ministry of Economy, Trade and Industry set rules in 2010 that required refiners to increase their residue cracking ratios by the end of last month.

Most companies decided to close crude distillation units rather than invest in costly cracking facilities, which maximize output of high-value products such as gasoline and diesel.