Spare parts with fixed prices were used in more than 20 models of Honda, Toyota, Nissan, Suzuki and Ford cars, the commission said.

In July, Japanese automakers' combined market share continued to drop, to 15.43 percent of the total passenger vehicle sector, compared with more than 20 percent in 2012, according to the China Association of Automobile Manufactures.

Major Japanese automakers all saw sales decline, while China's passenger vehicle sector reported an 11.5 year-on-year sales growth during the low season.

"China's enforcement of the Anti-Monopoly Law is in line with international practice," said Deng Zhisong, an attorney at Dacheng Law Office in Beijing.