SoftBank reportedly took a 20% stake in Coupang, Korea's largest mobile commerce company, boosting its overall funding to about $1.5bn.

Telecommunications and internet company SoftBank agreed today to invest $1bn in Korea-based e-commerce company Coupang, and will take a 20% stake in the business, according to Forbes.

Founded in 2010, Coupang’s app has been downloaded more than 25 million times, and it claims to be Korea’s largest mobile commerce company. The company’s main selling point is its same-day delivery service, and its direct retail revenues have more than tripled over the past six months.

The investment will be used to upgrade Coupang’s end-to-end fulfilment service and same-day delivery network, and to support the expansion of research and development centres in Silicon Valley, Seattle, Shanghai and Seoul.

Nikesh Arora, vice chairman of SoftBank, said, “Coupang is one of the fastest-growing and most disruptive internet companies in the world. Coupang is setting a new standard for how e-commerce can and should be done across the globe with its innovative technologies and approach to same-day delivery, mobile commerce, and customer service.

“We look forward to working with Bom Kim and his talented team and are excited to support their continued expansion.”

SoftBank’s investment increased Coupang’s total funding to about $1.5bn. It secured $300m from BlackRock Private Equity Partners, Wellington Management Company, Greenoaks Capital Management and Rose Park Advisors in December 2014 at a reported valuation of more than $2bn.

Sequoia Capital had led a $100m round raised by Coupang in May 2014 that also featured existing investors Greenoaks Capital, the Rose Park-owned Disruptive Innovation Fund and LaunchTime, and which was reportedly raised at a valuation above $1bn.

The funding, which represents the largest single investor yet made by SoftBank, is expected to close next month.