NOV. 14 9:57 P.M. ET Demonstrators stormed a Wal-Mart on the outskirts of Mexico City on Tuesday, accusing the U.S.-based retailer of selling low-cost goods at the expense of workers, farmers and public markets.

About 250 protesters chanted "Out! Out!" in front of Wal-Mart's corporate headquarters before entering the adjacent store, where they blocked aisles for about 30 minutes before leaving. There were no immediate reports of arrests, injuries or damage.

Ruben Garcia, a Mexican citizen who works with San Francisco-based activist group Global Exchange, said the discount chain's low prices take business away from the country's traditional public markets and depress wages for workers and farmers.

"If a cantaloupe costs 20 cents at a Wal-Mart, imagine how much the rural farmers are getting for this cantaloupe," Garcia said. "There is a high cost for the low prices." The company denied the accusations.

"Wal-Mart of Mexico generates very positive benefits for the country," it said in a statement. With more than 140,000 workers, Wal-Mart is the largest private sector employer in Mexico.

Some protesters carried signs bearing pictures of Andres Manuel Lopez Obrador, the leftist presidential candidate who claims he was robbed of victory in July elections and plans to be inaugurated as the "legitimate president" of an alternative government on Monday.

Lopez Obrador aides have accused Wal-Mart of supporting his conservative rival and the current president-elect, Felipe Calderon. The company denies the allegation.

The Arkansas-based company has been targeted by Mexican protesters before.

In 2004, a Wal-Mart-owned discount store opened less than a mile from the ancient temples of Teotihuacan, just north of Mexico City, despite months of protests by some residents who claimed the sprawling complex was an insult to Mexican culture.

Last month, Wal-Mart won preliminary approval over opposition from some residents to build a store in Cabo San Lucas, in Baja California Sur -- the only one of Mexico's 31 states where it currently does not have an outlet.