Alibaba Group has bought a 16.5% stake in Chinese video site Youku Tudou, which is similar to Google's YouTube.
Alibaba and Yunfeng Capital, a private equity firm co-founded by Alibaba executive chairman Jack Ma, have agreed to pay $1.22bn (£724m, €879m) for a combined 18.5% stake in Youku.
The deal is the latest strategic investment by Alibaba and Ma ahead of the firm's planned floatation in the US, which is expected in the coming weeks.
The Youku deal - a move that will help Alibaba step up its focus on online video - has brought the Chinese e-commerce giant's pre-IPO deal making spree to about $4bn in just six months.
Alibaba and Yunfeng are paying $30.50 per American Depositary Receipt of Youku, or a 26.3% premium over the last traded price, Youku said on 28 April.
Alibaba chief executive Jonathan Lu will join Youku's board.
"Alibaba's investment will strengthen Youku Tudou as China's largest online video platform and further differentiate our services and user experience," Youku chief executive Victor Koo said in a statement.
Alibaba's planned flotation, the largest US listing, could value the Chinese internet firm at as much as $120bn.
Alibaba could raise some $16bn through the proposed stock sale.
Competition is fierce in the world's largest Internet market, China, and Alibaba and Ma have made several strategic investments ahead of the firm's forthcoming IPO.
Earlier in the month, Ma and Alibaba co-founder Simon Xie picked up a 20% stake in Wasu Media for 6.54bn yuan ($1.05bn). Wasu, a cable and TV company, also manufactures Internet TV set-top boxes.
Alibaba in late March picked up a 10% stake in Hong Kong-listed Chinese department store operator Intime for $692m, a deal expected to provide Alibaba's e-commerce platform a brick-and-mortar extension.
Earlier in March, Alibaba paid $215m for a minority stake in mobile messaging app maker Tango.
Alibaba has also acquired a controlling stake in ChinaVision Media Group for $804m, giving it access to content including games, films and English Premier League Soccer.
Ma, who founded Alibaba in 1999, is worth an estimated $13bn.
Business tranactions under the ambit of Alibaba's sites were equal to some 2% of China's GDP in 2012; by comparison, Walmart's 2013 sales were equivalent to about 0.03% of US GDP.