China's auto sales accelerated by an annual 28 percent in May to notch the slowest pace over the past 13 months, according to China Association of Automobile Manufacturers.

Car makers sold a total of 1.43 million vehicles last month, bringing total sales during the first five months to 7.6 million units, up 53 percent from a year earlier, CAAM said in a statement.

Passenger car sales rose 26 percent to 1.04 million units while 395,100 commercial vehicles, or up 36 percent, were sold last month.

However, May's sales growth fell from a 124 percent increase in January and a 56 percent rise in March.

In addition, overall sales also continued to post negative growth on a monthly basis since March with a 7.5 percent decline from April. Passenger cars sales fell 6 percent from a month earlier.

After last year's breathtaking growth in vehicle sales, CAAM said growth would gradually slow to a more reasonable pace due to the higher comparative base. But it forecast vehicle sales in China this year to still top 15 million units, about 10 percent higher from 2009.

Demand to buy cars also cooled due to the sluggish stock and property markets, Rao Da, secretary of the China Passenger Car Association, pointed out. He estimated monthly sales would decline till August and car makers would offer bigger discounts to attract business.