The startup behind hit online social games Farmville, Zynga Poker, and Mafia Wars yesterday ramped up the pay-off for its more than 250 million players.

Zynga used a South By Southwest Interactive festival in Texas as a stage to unveil a new rewards programme for its titles, which have won legions of followers at Facebook and elsewhere on the internet.

Players who sign up online at website rewardville.com can shift winnings such as virtual goods, status or money between different games and use rewards to help out friends playing other Zynga games.

“With RewardVille, our aim is to delight players by rewarding them with new Zynga-level points and exclusive limited edition virtual items,” said Zynga vice president Roy Sehgal.

Later this week, Zynga will host its first live poker tournament with players of the online game invited to test their mettle in Las Vegas.

“The goal of our first live poker event and tournament is to bring Zynga Poker fans from Facebook to the felt,” Zynga Poker general manager Laurence Toney said of the reasoning behind the two-day tournament.

Zynga was founded in July 2007 in San Francisco by Mark Pincus, who named the startup after his late American bulldog Zinga.

Zynga boasts more than a quarter of a million players. Its titles include CityVille, FrontierVille, Café World, YoVille, and Vampire Wars.

The company is known for combining philanthropy and business, having raised more than $5 million for charitable causes through game play.

It is also one of a number of US technology giants offering digital ways to donate to Japan’s recovery from its massive earthquake and tsunami.

Zynga said it had raised $1 million in 36 hours for Save the Children’s Japan relief efforts by asking users to donate through the purchase of virtual goods in FarmVille, CityVille, FrontierVille and other games.