Pinterest valued at $1.5 billion with the help of Japan’s Rakuten

Pinterest has been valued at $1.5 billion, with the help a $100 million investment led by Japan's online retail giant Rakuten, Reuters reported on Thursday. 

The rapidly growing US-based bulletin-board social media website had previously been valued at $200 million after a funding round late last year, according to the Los Angeles Times. 

Rakuten said Thursday that shareholders Andreessen Horowitz, Bessemer Venture Partners, FirstMark Capital and a number of angel investors helped them raise capital for the Silicon Valley start-up, which allows users to "pin" photos from around the web up on virtual boards and follow other users, Financial Post reported. 

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Pinterest and Rakuten have entered into a partnership to expand the social media site's presence internationally, CNET reported.

"Our goal is to help people discover things they love, by connecting people through their shared interests," Ben Silbermann, co-founder and CEO of Pinterest, said in a statement, according to CNET. "Bringing Rakuten on board gives us an amazing opportunity to move a step closer to this goal." 

Rakuten's CEO Hiroshi Mikitani will serve as an advisor at Pinterest, as the company expands into Japan and Rakuten's 17 other markets, according to Reuters.

"It was one of the most hotly contested and sought-after financing events in Silicon Valley in quite some time," Mike Jaconi, a Rakuten executive who was involved in the negotiations, told Reuters.

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Pinterest has over 11 million unique visitors, according to surveys from earlier this year, with its strongest demographic being women in their 20s and 30s, Agence France Presse reported, and many see the site's potential to be used for e-commerce.

Rakuten's investment in the social media start-up comes amid Facebook's massive public offering this week, the largest IPO for an Internet company ever.