New York-based Union Square Ventures has gathered $350 million for two new funds, Fortune reported. The early backer of such technology firms as Twitter and Tumblr has already finalized commitments from institutional investors and paperwork for individual investors is already in its final stages, the report said.

Fortune reported that the $350 million will be evenly divided between Union Square Ventures' fourth early stage fund and its second "opportunities" fund which looks for opportunities in older, more established firms. The fund was originally aimed for a $300 million total, the report said.

Fred Wilson and Brad Burnham founded Union Square Ventures in 2004. Wilson is a veteran venture capitalist in New York City who managed Flatiron Partners before while Burnham was an investor in AT&T Ventures and was a co-founder of Tacoda, a company which was later bought by AOL, the report said.

Aside from Twitter, Tacoda and Tumber, other successful deals of the venture firm include Indeed.com, FeedBurner and Zynga. Japan's Recruit Co purchased Indeed.com while search giant Google bought FeedBurner. Its current portfolio comprises firms like Coinbase, Kicstarter, Foursquare and Shapeways, the report said.

Information from its website also revealed that Union Square Ventures gave seed funding to musician-focused technology platform Splice last year. It also gave Series A funds to Human Dx, Circleup and Kitchensurfing, among others, in 2013. The company describes itself as a "small collegial partnership that manages $650,000,000 across four funds."

In the year ending February last year, the funds of Union Square Ventures had a 64% aggregate internal rate of return or IRR which makes it one of the most successful venture companies in the past decade. Its 2004 had an IRR of 66.96% while its 2008 fund posted an IRR of 38.88%. Its 2012 fund had a 29.04% IRR while its first opportunities fund posted an IRR of 61.44%, the report said.