Mobile location based start-up Foursquare raised $50 million in a round of financing lead by venture capital firm Andreessen Horowitz, the company said on Friday.

With this latest round of funding, the New York-based company is valued at about $600 million, according to a source familiar with the deal.

O'Reilly AlphaTech Ventures, Union Square Ventures and Spark Capital are also involved in the round.

We're excited to announce that we've closed a round of funding that will enable us to hire more engineers, evolve our merchant offerings and continue our international expansion, Foursquare Chief Executive and co-founder Dennis Crowley wrote in an e-mail.

Foursquare offers a mobile application that allows its 10 million users to check in to area establishments and share those check ins with their social network of friends.

The company drives users to local restaurants, bars, retail outlets and other places by offering discounts.

On Thursday, Foursquare announced that it expanded its relationship with American Express nationally, allowing American Express card members to link their Foursquare profiles to their cards in order to redeem specials and discounts.

The technology blog TechCrunch first reported the deal.

(Reporting by Jennifer Saba; editing by Carol Bishopric)