After weeks of rumors, DST’s investment in Twitter was confirmed officially for the first time yesterday on Twitter’s blog.

“Now we have an opportunity to expand [our] reach with a significant round of funding led by the venture firm DST Global, along with the participation of several of our existing investors,” Twitter writes. “We will use these resources to aggressively innovate, hire more great people, and invest in international expansion.”

No details of the transaction have been disclosed officially, but the Financial Times reported today from “one person familiar with the transaction” that DST’s investment amounted to $400 million for just a 5% stake. The deal thus brings Twitter’s total valuation to $8 billion. US mutual fund concern T Rowe Price and an internet fund managed by JP Morgan are said to lead a group of other investors.

Not only has DST been – through its funds DST Global I and II – Russia’s largest Internet-oriented investment fund, it has stakes in a number of leading international Internet companies. Its total investment in Facebook reached over $500 million, with a stake estimated at 10% in late 2010 before new investments made in early 2011. The Russian fund also has stakes in Zynga, Groupon, Spotify and Chinese e-commerce platform 360buy.com.

DST is tightly connected to Mail.ru Group, the Russian Internet giant that began trading on the London Stock Exchange in October 2010.