NEW YORK (REUTERS) - Walmart Inc, the nation's largest retailer, said on Tuesday (Sept 3) that it would stop selling ammunition for handguns and some assault-style rifles in all its stores across the United States, and called for action on gun safety after a string of mass shootings, including at Walmart stores in Texas and Mississippi.

Walmart also called for a strengthening of background checks for gun buyers and action to take guns out of the hands of those who pose a risk of violence, which was followed by an almost identical message from grocery operator Kroger.

Both Walmart and Kroger, which exited the firearms and ammunition business last year when its Fred Meyer unit stopped such sales, said they are now asking customers not to bring guns into their stores, even when allowed by local laws.

The two retailers are among a growing number of US companies, such as Delta Air Lines and Bank of America, that are responding to the debate over guns and gun safety as mass shootings proliferate, risking backlash from powerful gun owners' groups while elected leaders consider options.

"It's clear to us that the status quo is unacceptable," Walmart's chief executive officer, Mr Doug McMillon, said in a letter to employees. "As a company, we experienced two horrific events in one week, and we will never be the same."

Kroger, in a statement from corporate affairs vice-president Jessica Adelman, spoke about "the growing chorus of Americans who are no longer comfortable with the status quo and who are advocating for concrete and common sense gun reforms".

It said it was "joining those encouraging our elected leaders to pass laws" on background checks and keeping firearms out of the hands of those at risk for violence.

Mr McMillon said Walmart's decision follows his visit to El Paso, Texas, on Aug 6, three days after a gunman went on a rampage at a Walmart store there, killing 22 people.

Walmart said it would stop selling ammunition for handguns and some assault-style rifles in all its stores across the US. Mr McMillon, in the letter, described himself as a gun owner and said that company founder Sam Walton was "an avid outdoorsman who had a passion for quail hunting". Walmart would stop selling handgun sales in Alaska, the only state where it still sells hand guns. The halt on the ammunition and handgun sales will come into effect when current inventory is sold out.

Kroger had sold guns in 43 of its Fred Meyer stores in the Pacific Northwest and Alaska before announcing in March 2018 that it would exit the firearms business.

The retailers' latest moves sparked immediate reaction from groups on both sides of the gun control debate.

"The tide is turning," said Ms Shannon Watts, founder of Moms Demand Action, a gun control advocacy group. The announcements "send a strong cultural signal that when lawmakers don't protect their constituents, companies will protect their customers".

The National Rifle Association (NRA), a pro-gun group with deep political ties, said Walmart was succumbing to pressure from "anti-gun elites".

"Lines at Walmart will soon be replaced by lines at other retailers who are more supportive of America's fundamental freedoms," it said. It did not immediately respond to a request for comment on the Kroger move.

Walmart said its latest actions would reduce its share of the ammunition market from around 20 per cent to a range of about 6 per cent to 9 per cent, and would trend towards the lower end of that range over time.

US gun and ammunition stores had total sales of about US$11 billion (S$15.3 billion) last year, of which 19 per cent was ammunition, according to market research firm IBISWorld.

The move reflects growing corporate activism on guns.

Walmart, like rival Dick's Sporting Goods, had previously ended sales of assault rifles and raised the minimum age for gun purchases to 21.

Bank of America last year said it would no longer lend to companies making military-style firearms for civilians, and airlines Delta and United last year said they were no longer offering discounted rates to the NRA.

The latest move will leave Walmart focused on weapons for hunting, including deer rifles, shotguns and related ammunition.

"The general principle is if we don't sell the firearm, we wouldn't sell the ammunition," a spokesman for Walmart told Reuters.

Just last month, Walmart said it would not change its policy on selling firearms even as it took down signs and playable demos of violent video games.

Last Friday, Mr McMillon in his letter to employees said he would send letters urging action on "common sense measures" to the White House and the Congressional leadership, calling for debate of the reauthorisation of a ban on assault weapons, to determine its effectiveness, as well.