Coffee chain Starbucks Corp has asked customers in the United States to leave their guns at home, after being dragged into an increasingly fractious debate over gun rights in the wake of multiple mass shootings.

While many US restaurant chains and retailers do not allow firearms on their properties, Starbucks' policy had been to default to local gun laws, including "open carry" regulations in many US states that allow people to bring guns into stores.

In August, this led gun-rights advocates to hold a national "Starbucks Appreciation Day" to thank the firm for its stance, pulling the company deeper into the fierce political fight.

Locations for Starbucks Appreciation Day events included Newtown, Connecticut, where 20 children and six adults were shot dead in an elementary school in December. Starbucks closed that shop before the event was scheduled to begin.

The Seattle-based company plans to buy ad space in major national newspapers, including The New York Times, Wall Street Journal, Washington Post and USA Today on Thursday to run an open letter from Chief Executive Howard Schultz explaining the decision.

Schultz said in the letter to customers late on Tuesday that Starbucks Appreciation Day events "disingenuously portray Starbucks as a champion of 'open carry'. To be clear: we do not want these events in our stores."

The coffee chain did not, however, issue an outright ban on guns in its nearly 7,000 company-owned cafes, saying this would potentially require staff to confront armed customers.

The company hoped to give "responsible gun owners a chance to respect its request", Schultz said.

The CEO said the policy change was not the result of the Newtown Starbucks Appreciation Day event, which prompted the Newtown Action Alliance to call on the company to ban guns at all of its US stores. Nor was it in response to the mass shootings this week at the Washington Navy Yard.

"We've seen the 'open carry' debate become increasingly uncivil and, in some cases, even threatening," Schultz wrote, noting that "some anti-gun activists have also played a role in ratcheting up the rhetoric and friction", at times soliciting and confronting employees and patrons.

"We found ourselves in a position where advocates on both sides of the issue were using Starbucks as a staging ground for their own political position," said Schultz, who in the past has willingly waded into the public debate over the US national debt and gay marriage.

Schultz said more people had been bringing guns into Starbucks shops over the last six months, prompting confusion and dismay among some customers and employees.

"I'm not worried we're going to lose customers over this," he said. "I feel like I've made the best decision in the interest of our company."

Starbucks' request does not apply to authorized law enforcement personnel.

Reuters—AP