Starbucks has found itself in the middle of a public relations disaster in the United States after an incident in one of its Philadelphia stores last week that saw two African American men arrested went viral.

Starbucks chief executive Kevin Johnston has issued a statement unreservedly apologising to the men, who were handcuffed by half a dozen police officers in an outlet last Thursday following a dispute with a store manager.

The men, who were waiting for a friend, were asked to leave after using the bathroom without making a purchase but refused, at which time the manager called 991, local police said.

A video of the arrest was shared millions of times on social media over the weekend, sparking calls to boycott the coffee chain and protests outside of its stores.

@Starbucks The police were called because these men hadn’t ordered anything. They were waiting for a friend to show up, who did as they were taken out in handcuffs for doing nothing. All the other white ppl are wondering why it’s never happened to us when we do the same thing. pic.twitter.com/0U4Pzs55Ci

— Melissa DePino (@missydepino) April 12, 2018

In a public statement Johnstone said the incident led to a “reprehensible outcome” and that he would be personally overseeing a review of Starbuck’s training processes.

“We have immediately begun a thorough investigation of our practices. In addition to our own review, we will work with outside experts and community leaders to understand and adopt best practices,” he said.

“The video shot by customers is very hard to watch and the actions in it are not representative of our Starbucks mission and values.

“Regretfully, our practices and training led to a bad outcome—the basis for the call to the Philadelphia police department was wrong,” Johnston continued.

Johnstone has offered to meet the two men in person to offer a face-to-face apology.

We apologize to the two individuals and our customers for what took place at our Philadelphia store on Thursday. pic.twitter.com/suUsytXHks — Starbucks Coffee (@Starbucks) 14 April 2018

Philadephia mayor Jim Kenney said the incident exemplified an example of racial discrimination, adding that he has referred the matter to the Philadelphia commission on human relations.

“I am heartbroken to see Philadelphia in the headlines for an incident that — at least based on what we know at this point — appears to exemplify what racial discrimination looks like in 2018,” he said in a statement.

I’m very concerned by the incident at Starbucks. I know Starbucks is reviewing it and we will be too. @PhillyPolice is conducting an internal investigation. https://t.co/fp0NjwiO2L

— Jim Kenney (@PhillyMayor) April 14, 2018

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