TOKYO -- After years of fierce competition in Southeast Asia, Chinese online retailers are gearing up to tap more mature markets in North America and Europe.

Alibaba Group Holding launched a new platform, Miravia, in Spain in December to target middle- and high-income earners, while its AliExpress is struggling to gain traction in the U.S. Rival Pinduoduo is reportedly preparing to launch its Temu e-commerce site in Canada and Spain, following its entry into the American market last September.