Publicity photo of Zynga CEo Mark Pincus and wife Ali following the ringing of the opening bell for the NASDAQ exchange in San Francisco
Zynga CEO Mark Pincus and his wife Ali are shown after Pincus rung the opening bell of the NASDAQ exchange remotely from Zynga's headquarters on the day of the company's IPO in San Francisco, December 16, 2011. REUTERS

(REUTERS) -- Zynga shares fell as much as 13 percent below their IPO price, in their second trading session, as investors worried about the online game publisher's growth prospects.

Analysts said Monday's sell-off, following the initial public offering at $10 per share on Thursday, mirrors the double-digit stock decline of Japanese game maker Nexon since it went public last Wednesday in Tokyo.

Investors aren't interested in Zynga - not at these prices, said Sterne Agee analyst Arvind Bhatia. The demand post-IPO is what drives the stock price and it's just not there.

With these latest losses, Zynga has a market value of $7.8 billion, down from $8.9 billion when it went public. Investors are balking at the company's heavy dependence on leading social networking website Facebook and slowing revenue growth in recent quarters, Bhatia added.

Investors had eagerly awaited the IPO as a way to get a slice of Facebook's growth before the website goes public, possibly in 2012. Zynga makes money on Facebook by selling virtual items such as jewelry and poker chips in its games such as FarmVille and CityVille.

Zynga's stock performance could hurt other private companies waiting to go public, such as Yelp and even Facebook, analysts said.

Zynga fell as low as $8.75, before trading down about 5 percent at $9.04 on Nasdaq shortly after midday.

(Reporting By Liana B. Baker)