Two executives of Wal-Mart Stores Inc's China operation, including its head, have resigned, the company said in a statement on Monday.

Chief executive Ed Chan has resigned for personal reasons, it said.

Clara Wong, senior vice president of People of Walmart China, has also stepped down, it said without giving further details.

The resignations come after the world's largest retailer temporarily closed more than a dozen stores in a city in western China amid accusations that Wal-Mart mislabelled ordinary pork as organic over the past two years.

Authorities in Chongqing have detained 37 Wal-Mart employees and arrested two over the incident.

We recently celebrated our 15th anniversary in China, and there is a lot to celebrate about our business here, Scott Price, CEO of Walmart Asia who will also serve as the interim China head, said in a statement.

China is a very important market for Walmart and China's 12th five-year plan will provide strong opportunities to the retail industry.

Wal-Mart competes with French hypermarket chain Carrefour , Britain's Tesco , Germany's Metro AG , China's Sun Art <6808.HK> and China Resources Enterprise <0291.HK> in a hypermarket sector that is forecast to grow at a compounded annual rate of 10.1 percent between 2010 and 2015, according to Euromonitor.

After entering China in 1996, its expansion gathered steam in 2007 when the world's largest retailer bought a 35 percent stake in Taiwanese hypermarket chain Trust-Mart. It has 353 stores in the mainland.

Wal-Mart's market share in the hypermarket space stood at 11.2 percent in 2010, in second place after Sun Art, but spending involved in the expansion has been weighing on its profitability.

Other major Western firms have recently come under increasing scrutiny from China's state media, facing fiery criticism over hot issues like food safety and garment quality.

(Reporting by Kazunori Takada; Editing by Jacqueline Wong and Ken Wills)