Hyundai Motor Group, South Korea's top automotive group, acquired the largest number of patents on clean energy technology in the United States in the third quarter of 2015, the Clean Energy Patent Growth Index showed Monday.

Among 916 clean energy patents registered with the U.S. Patent and Trademark Office in the July-September period, the combined patents by Hyundai Motor Co. and its company Kia Motors Corp. ranked top with 54, according to the index released by the Cleantech Group.

Japan's Toyota came next with 41, trailed by U.S. automaker Ford with 36 and Japan's Honda with 31 during the period, said the group under Heslin Rothenberg Farley & Mesiti, a New York-based law firm dedicated to intellectual property law.

The number of patents by automakers accounted for 20.5 percent of the total, or 188, mostly related to hybrid and electric vehicles as well as fuel cells aimed at developing eco-friendly cars, it said.

As of March, the Hyundai Motor Group had 2,745 domestic and 6,945 overseas patents, its regulatory filing showed. (Yonhap)