MEXICO CITY (Reuters) -Walmart's Mexico unit on Thursday posted a 5% year-on-year rise in its second-quarter net profit, boosted by slightly higher sales especially in June, though earnings were slightly behind forecasts.

Walmart de Mexico, the biggest retailer in Mexico, posted a net profit of 11.44 billion pesos ($668 million).

The company posted a profit of 0.66 pesos a share, just below the Refinitiv estimate of 0.69 pesos.

Quarterly revenue at the chain rose 9.25% from the year-ago period to reach 213.724 billion pesos, boosted by a "Hot Sale event" in June, the company said in a statement, also marginally beating a Refinitiv estimate of 213.34 billion pesos.

It also saw a boost during its summer "heat wave" campaign, it said, as the North American country faced a three-week-long atypical heat wave in June that sent temperatures soaring.

Same-store sales increased 8.5% in Mexico and 9.5% in Central America.

Earnings before interest, tax, depreciation and amortization (EBITDA) for the quarter rose 8.5% to 21.9 billion pesos.

The firm said its gross merchandise volume (GMV), a widely watched figure for the e-commerce industry's performance, rose 25% in Mexico, while sales in ecommerce increased 21%.

It also expanded its physical footprint with 22 new stores in Mexico.

($1 = 17.1156 pesos at end-June)

(Reporting by Carolina Pulice and Noe Torres; Editing by Isabel Woodford and Lincoln Feast)