Amazon and Walmart are in war over worker pay — and now corporate taxes.

After Amazon CEO Jeff Bezos on Thursday issued a challenge to other retailers, not naming which ones specifically, to match Amazon's pay and benefits, Walmart has responded, albeit quietly.

"Today I challenge our top retail competitors (you know who you are!) to match our employee benefits and our $15 minimum wage. Do it! Better yet, go to $16 and throw the gauntlet back at us. It's a kind of competition that will benefit everyone," Bezos wrote in his annual letter to shareholders.

Walmart's executive vice president of corporate affairs, Dan Bartlett, then shared an article Thursday morning on Twitter about Amazon paying $0 in federal taxes on more than $11 billion in profits last year. He wrote: "Hey retail competitors out there (you know who you are) how about paying your taxes?"

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The CEO of eBay, Devin Wenig, also snapped back at Amazon on Thursday, writing on Twitter: "I'll dedicate my [shareholders] letter to customers, purpose and strategy."

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A spokesperson for Amazon said in a statement to CNBC:

Amazon pays all the taxes we are required to pay in the U.S. and every country where we operate, including paying $2.6 billion in corporate tax and reporting $3.4 billion in tax expense over the last three years. Corporate tax is based on profits, not revenues, and our profits remain modest given retail is a highly competitive, low-margin business and our continued heavy investment. We have invested more than $160 billion in the U.S. since 2011, building a network of more than 125 fulfillment and sortation centers, air hubs and delivery stations as well as cloud-computing infrastructure and wind and solar farms. We invest heavily in research and development at our Seattle headquarters and 18 tech hubs across the country. We are creating tens of thousands of quality jobs each year with industry-leading pay for people of all skill levels, bringing our total workforce in the U.S. to more than 250,000.

Watch: How Amazon paid no federal income tax in 2018