Walmart has announced the resignation of key executives from its online business. Eduardo Castro-Wright, vice-chairman of global sourcing operations, is to retire in July and Wan Ling Martello, vice-president of ecommerce, is to leave the company to take up a new position at Nestlé. The departures come amid a drive by Walmart to push more customers to make purchases on the internet. Walmart chief executive Mike Duke said the company was focusing on improving the online site as more shoppers migrate to the web and like-for-like sales at US stores decline. Walmart acquired ecommerce company Kosmix and created @WalmartLabs as part of the online strategy. The company is also testing home delivery of fresh groceries ordered online.