* Central American same-store sales up 8.1 percent
* Twenty stores opened in Mexico last month
MEXICO CITY Oct 8 (Reuters) - Mexico's biggest retailer Wal-Mart de Mexico said on Monday that sales at its Mexican stores open for at least a year rose 10 percent in September from a year earlier.
The r esults exceeded the expectations of 7 percent growth in a Reuters survey of five sector analysts.
Walmex , an affiliate of top global retailer Wal-Mart Stores Inc, said it operated 2,224 stores in Mexico and 633 in Central America at the end of September after opening 20 stores in Mexico last month and two in Central America.
Sales at Central American stores open for at least a year in September rose 8.1 percent, year on year.
Walmex shares, down nearly 18 percent from an April high following news of a probe by U.S. authorities over allegations it used bribes to speed store openings, rose 0.87 percent on Monday to 37.31 pesos be fore the sal es results were disclosed.