TOKYO — Japanese fashion giant Uniqlo said on Tuesday (Jan 16) that it is suing Chinese rival Shein over copycats of a massively popular crossbody pouch dubbed online the "Mary Poppins carryall".

Videos of fans praising its deceptively small size have gone viral on social media, with one clip on TikTok of a young woman unpacking numerous large items racking up more than a million views.

The lawsuit filed in Japan against Shein Japan and two subsidiaries "demands the immediate cessation of sales of the imitation products, and compensation for damages incurred," Uniqlo said in a statement.

The nylon Round Mini Shoulder Bag, retailing for US$19.90 (S$27) in the United States, has reportedly become Uniqlo's best-selling bag ever, repeatedly selling out.

Shein, founded in 2008 in China and based in Singapore, has quickly conquered the global fast fashion market by catering to young customers through social media. 

Valued at US$66 billion last year with revenues reportedly over US$23 billion, the online retailer is eyeing a major initial public offering in New York potentially this year, the Wall Street Journal reported in November.

The firm has been accused of exploiting unpaid labour, obscuring production processes and encouraging overconsumption as it faces the wrath of environmental and human rights activists.

Last month, Chinese-owned online retailer Temu sued Shein in a US court, accusing it of "mafia-style" intimidation tactics to keep the upper hand in the local market.

Shein Japan was not immediately available for comment on Tuesday. AFP