Hyundai Motor Co. and its smaller affiliate Kia Motors Corp. saw their share in the Chinese market decline on-month in May, industry data showed Tuesday, amid fierce competition in the world's No. 1 car market.

Hyundai and Kia registered a combined market share of 9.1 percent in May, down 0.9 percentage point from the 10 percent posted a month earlier, according to the data.

The duo thus surrendered its one-month-long title as the No. 2 car seller in China to General Motors Co.

The decline came as Hyundai and Kia, the flagships of the world's No. 5 auto giant Hyundai Motor Group, saw their sales drop last month.

The two carmakers' sales in the world's second-largest economy stood at 129,000 units in May, down 9.8 percent from a year earlier.

Hyundai's sales plummeted 12.1 percent on-year, and Kia's shipments also withdrew 5.9 percent, according to the data.

"Sales have been slow mostly with our past models in China, but we'll be able to recover the 10-percent market share level once the new edition of the Tucson sport utility vehicle is launched there later this year," a Hyundai Motor official said.

Hyundai Motor Group's two carmakers have been pushing to tap deeper into the Chinese market by expanding plants there amid fierce competition from both local and global brands.

Hyundai was to break ground for its fifth plant in China in the country's southwestern city of Chongqing later Tuesday. (Yonhap)