Finland's Rovio Mobile, known for its Angry Birds puzzle video game, unveiled on Friday payment software that gives mobile telecom operators a chance to win a share of booming app store business.

Mobile operators have struggled to grab a piece of the mobile applications market -- worth $4.1 billion last year, according to research firm Chetan Sharma -- as consumers pay with credit cards directly to Apple Inc or Google Inc.

Rovio said it would start to roll out its payment solution in early 2011 for Android phones sold by Finland's top mobile carrier, Elisa, for purchasing additional features in Angry Birds. This gives operators some revenue, compared to none. We are going to open it up to all other developers, said Peter Vesterbacka, head of Rovio's business development in North America.

Vesterbacka said the company had seen strong interest toward payment software, which enables simple purchasing charged on a user's phone bill.

Angry Birds has topped the charts of paid-for Apple apps for months in about 60 countries including the United States and Britain.

Vesterbacka said Angry Birds reached 50 million downloads on Friday, 12 months after the game was launched. It aims to reach 100 million downloads by mid-2011.

It took Tetris 20 years to reach the 100 million milestone, he said.

Angry Birds -- in which players have to help the birds destroy pigs who stole their eggs, with the help of a slingshot -- has broken new ground in mobile gaming by staying at the top of the charts, unlike most hit mobile games whose popularity diminishes over time.

(Reporting by Tarmo Virki, editing by Matthew Lewis)