MEXICO CITY, Oct 28 (Reuters) - Walmart's Mexico unit will open stores under a new "Walmart Express" brand beginning in November, and gradually convert all existing Superama grocery stores to the format, it said on Wednesday.

The move will give the country's biggest retailer another brand alongside its Walmart, Sam's Club and Bodega Aurrera chains, as it focuses on ramping up e-commerce. Superama stores, while varied in size, are typically much smaller than the flagship Walmart shopping centers and sell only groceries.

As with its other formats, Walmart Express customers will be able to place orders online for pickup or delivery, said Walmart de Mexico, also known as Walmex.

"Operations of Walmart and Walmart Express will share best practices, both in stores and online, with a gradual alignment of their e-commerce platforms," the retailer said in a statement.

Walmart de Mexico reported that online purchases in Mexico grew more than 200% in the third quarter to make up 3.8% of total sales in the country, as pandemic restrictions led to a flurry of e-commerce shopping.

Walmart Express stores will be deployed to areas of Mexico where the retailer does not yet have a presence, Walmart said. It did not give a timeline for the Superama renovations. (Reporting by Daina Beth Solomon; Editing by Kirsten Donovan)