BEIJING, June 18 -- Lululemon has issued a public apology after a promotional event at China's Great Wall ignited a social media firestorm over the use of a Japanese Taiko drum during what was intended as a celebration of Chinese culture.

The athleisure giant said it was "deeply reflecting" on the incident after criticism erupted online following its May 30 yoga festival at the landmark.

The event featured Chinese actor and brand ambassador Zhu Yilong leading participants through yoga and Tai Chi before joining the HiiKo Drum Group for a performance.

But musicians and online critics quickly argued that the instrument used was not a traditional Chinese Dagu drum as presented, but a Japanese Taiko drum.

According to CNA, Chinese percuss...