South Korea police raid Starbucks HQ over 'Tank Day' fiasco

South Korean police raided the Starbucks national headquarters Wednesday, the chain's local operator told AFP, following allegations an advertising campaign defamed activists slain in 1980 pro-democracy protests.

Starbucks Korea caused an uproar this year when it launched a "Tank Day" promotion on May 18, touting a new line of capacious tumblers for its coffee beverages.

The date marked the anniversary of the 1980 Gwangju pro-democracy uprising, when at least 165 civilians were killed as a military dictatorship rolled tanks out onto the streets.

The chain was accused of trivialising the nation's landmark protest movement and insulting the dead, remembered as martyrs by many South Koreans.

A civic group and bereaved families filed a complaint accusing members of the Shinsegae Group, which operates Starbucks Korea, of defaming and insulting the victims and relatives.

"The Seoul police raided the headquarters of Starbucks Korea this morning as part of the ongoing investigation," a Shinsegae Group spokesman told AFP, declining to provide further details.

Starbucks Korea said in a statement: "We can confirm that an investigative authority conducted a search and seizure today. We understand this to be part of an ongoing investigation."

Seoul police said an investigation into the firm was ongoing, but also declined to provide further information about the case.

The complaint named Shinsegae Group chairman Chung Yong-jin and Son Jung-hyun -- the former CEO of Starbucks Korea, who resigned over the furore.

The advertising fiasco also alluded to phrases which officials at the time used to dismiss allegations they had tortured a student activist to death.

South Korea is the third-largest market for the coffee giant, behind the United States where it was founded, and China.

The controversy prompted a public apology and the one-off early closure of the chain's more than 2,000 stores nationwide for staff education in June.

The Shinsegae Group has previously said its own internal investigation found no evidence of intentional wrongdoing.

But it admitted its audit suffered from limitations, such as the executive in charge of planning the campaign refusing to surrender their mobile phone.

Police investigators are hunting for evidence which was not included in the company's own investigation, according to the Yonhap News Agency and national broadcaster KBS.

The so-called Tank Day controversy led to a "sharp decline in sales" in the early days of the scandal, according to the Shinsegae Group.

Starbucks' estimated credit and debit card payment volume fell 17 percent from May to June, according to local data platform firm IGAWorks.