Sales at McDonald's restaurants dropped in August, hurt by a food-safety scandal in China and heavy competition in the US, the company said Tuesday.

The US fast-food giant said global comparable sales fell 3.7 percent in August, bigger than the 2.5 percent decline in July.

"During August, McDonald's global business faced several headwinds that impacted sales performance," said chief executive Don Thompson.

Sales sank 14.5 percent in the Asia/Pacific, Middle East and Africa region, which accounts for about one-fourth of McDonald's revenues.

McDonald's did not release revenue figures for August. In the second quarter, the fast-food company reported global revenues of $7.2 billion.

In July, Chinese officials shut food-supplier Shanghai Husi Food Co. following a television report alleging the plant mixed out-of-date meat with fresh product that was then supplied to McDonald's.

The restaurant chain also curtailed Japanese sales of products made with chicken from China in the wake of the debacle.

McDonald's said it expects the China food safety problems will result in a drop in earnings of 15-20 cents per share in the third quarter compared to last year, when it notched $1.52 per share.

US comparable sales fell 2.8 percent in August due largely to "sluggish industry growth in a highly competitive marketplace," the company said.

European comparable sales declined 0.7 percent, with a strong performance in Britain offset by weakness in Russia.

In 2013, US sales accounted for about 30 percent of McDonald's global revenues, while European sales represented about 40 percent.

Dow member McDonald's fell 1.0 percent to $91.58 in mid-morning trade.