SAN FRANCISCO--Zynga, the social gaming company eyeing a lucrative IPO, has selected more Next Fifteen agencies to support its expansion in the US and UK.

The company, behind popular titles CityVille, Mafia Wars and Farmville, is understood to have tapped handed its US corporate mandate to The OutCast Agency. In the UK, meanwhile, it has tapped Lexis to build consumer awareness. Both firms secure the briefs following separate competitive reviews, as earlier revealed by the Holmes Report.

OutCast takes charge of the brief after previously handling projects for Zynga. Lexis becomes UK consumer AOR after sister Next Fifteen firm M Booth won Zynga’s US consumer duties earlier this year.

Last week, the All Things D blog reported that Zynga was “poised” to file for its initial public offering. The development comes after LinkedIn’s flotation raised $9 billion, sparking fears of a new tech bubble.

Zynga leads the nascent social gaming space, claiming 250 million users of its games - which are largely distributed via Facebook. All Things D reports that it generated $400m profit last year on $850m in revenue. It has rapidly grown to 1,500 employees across 13 offices in six countries.

Accordingly, the company’s need for a retained corporate PR agency in the US is not difficult to understand. Zynga’s most recent round of financing raised its valuation to approximately $10 billion. Previous investors in Zynga include Google, Softbank and DST.

In the UK, Zynga is aiming to drive its awareness as a platform for social games among consumer, business and tech outlets. The brief called for “out-of-the-box, creative proposals” to launch CityVille in the UK, among other initiatives.

Zynga global comms chief Dani Dudeck declined to comment.