Line Corp. and Mercari Inc. are joining forces on mobile payments as the nation's internet companies race to dominate cashless transactions in the world's No. 3 economy.

The operator of Japan's most popular messaging platform and the used-goods online marketplace app will let users shop and pay for purchases at stores that accept each other's systems, they told reporters in Tokyo on Wednesday. They also launched an alliance to welcome other mobile payment providers.

After years of inactivity, mobile payments competition is heating up in Japan. Line and Mercari are teaming up to take on powerful rivals: E-commerce giant Rakuten Inc. runs its own bank, has a credit card with more than 15 million customers and is building a mobile-phone network, while PayPay — backed by SoftBank Group Corp., Yahoo Japan Corp. and India's Paytm — sparked a shopping frenzy in December by giving users ¥10 billion ($90 million) in rebates on purchases.