Public relations representatives at both Recruit Co. Ltd. and Freelancer.com, one of the largest online staffing providers, declined to comment last week on speculation that talks are under way for Recruit to acquire Freelancer.com.

Techcrunch reported on Sept. 9 that Recruit made a $400 million offer to buy Freelancer.com.

Freelancer.com ranks among the four largest online staffing providers, according to research by Staffing Industry Analysts, with estimated 2012 revenue of between $100 million and $150 million. The Australia-based company was founded in 2004.

“Online staffing” refers to an online platform model that enables specific hirers and specific workers to enter into, complete and transact work arrangements. Other large firms in this space include Elance and oDesk.

Recruit Co. Ltd., based in Japan, ranks among the world’s largest staffing firms. And it has made several acquisitions as of late. Earlier this month, one of its U.S. divisions, The CSI Companies, acquired information technology staffing firm Anteo Group.

Recruit acquired one of India’s largest executive search firms in August; it acquired Bó Lé associates, one of Asia’s largest executive search firms in April. The company also acquired job search site Indeed in 2012. Recruit also acquired Staffmark Holdings Inc. and Advantage Resourcing Group in 2011 — both firms ranked on Staffing Industry Analysts’ lists of largest staffing firms. Recruit also acquired The CSI Companies Inc., which is based in Jacksonville, Fla., in 2010.

Recruit is reported to be in the process of putting forward an initial public offering in the future.