Japan's biggest fast-food chain operator, McDonald's Holdings Co (Japan), said on Wednesday that sales at restaurants open more than one year, or same-store sales, fell 11.1 percent from a year earlier.

Underlining the short-lived impact of an aggressive price-cutting campaign, all-store sales at the 50-percent-owned unit of U.S. fast-food giant McDonald's Corp (MCD) also sagged, dropping 7.4 percent from a year ago, the company said.

The falls mark a dramatic reversal from August, when sales at its total 3,886 stores rose 0.5 percent -- the first year-on-year increase in 11 months -- thanks to a cut in hamburger prices to a record 59 yen (48 cents) from 80 yen early in the month.

McDonald's said last month that 121.63 million people walked into its stores in August, up 9.5 percent year-on-year and equivalent to the entire population of Japan.

But the strategy to lure cost-sensitive Japanese consumers failed to last long. The company said the numbers of visitors also fell 5.5 percent from a year earlier in September.

The poor September results are likely to weigh on shares in the fast-food chain, which ended Wednesday before the announcement up 1.38 percent at 2,200 yen.

The stock has lost 33.7 precent in value from the start of this year, hit by a loss of customer appetite for beef due to worries over a mad cow disease outbreak despite reassurances that McDonald's uses only imported beef in Japan.

($1-124.08 Yen)