Russia-based online retailer Ozon.ru said today it has raised $100 million in financing from a group of investors that includes Rakuten Inc., the Japan-based e-marketplace operator that owns U.S. e-retailer Buy.com Inc. Rakuten, which has recently been on an international e-commerce investment run, did not say how much it invested or how big of a stake it will take in Ozon.

Ozon says the funding round was led by Russia-based investment firm Ru-Net Ltd., which participation also from Switzerland-based equity firm Alpha Associates, United Kingdom-based Index Ventures and Russia-based Baring Vostok Private Equity Fund, which first invested in Ozon in 2000.

Ozon did not specify how it plans to use the capital but said it will strengthen its operations and expand into new areas such as travel. Ozon, which bills itself as the Russian Amazon.com, sells such products as books, consumer electronics, mobile phones and toys. Ozon says it took in $137 million in revenue in 2010.

“We are pleased to form this partnership with Ozon.ru,” says Rakuten chairman and CEO Hiroshi Mikitani.  “They have committed leadership, a talented team and a deep understanding of the Russian market. Ozon.ru has built a highly successful e-commerce ecosystem and has focused expansion plans.”

After the purchase of Buy.com, No. 32 in the Internet Retailer Top 500 Guide, Rakuten has continued to make global e-commerce deals.

In June, for instance, it bought a 75% stake in Brazil-based Ikeda, which sells e-commerce technology and services to more than 100 of the largest online retailers in that country. And in July, it acquired 80% of Germany-based Tradoria GmbH, which sell an e-commerce platform used mainly by small- and medium-sized merchants.