The South Korean developer of wildly popular game PlayerUnknown’s Battlegrounds (PUBG) has removed controversial game elements referencing the imperial Japanese army and apologized, Xinhua reported Tuesday.

The report said that on Saturday, PUBG released a pilot mask emblazoned with the Rising Sun flag, and a non-player character identified as “Unit 731” — a notorious biowarfare research unit in the Japanese army that conducted lethal experiments on Chinese and Korean civilians during World War II.

The developer issued its apology on Sunday, after the imagery caught the attention of Korean gamers. Although the elements appeared in the Korean version of PUBG, Chinese players also added their voices to the chorus of criticism. (Image: Weibo)