Instagram co-founder Kevin Systrom
Instagram co-founder Kevin Systrom said in Paris recently that the move to pull Instagram photos from Twitter was based on a desire to increase Instagram's online presence. The company has about 100 million active accounts compared to Twitter's half-billion. Instagram is owned by Facebook, which has over a billion active accounts. Reuters

The battle for market share in social networking just got a little more heated as popular photo-sharing network Instagram surprised Twitter users by no longer making their photos visible on the micro-blogging service.

Before, subscribers to both services could post Instagram photos directly to their Twitter feed. Now, those photos have been replaced with links that send visitors to the subscriber’s Instagram feed.

“[Instagram] photos are no longer appearing in Tweets or user photo galleries,” San Francisco-based Twitter Inc. said in a statement. The change began to be implemented late last week.

To those who don’t use Instagram or don’t dabble heavily in social networking, this means nothing. But many of the 100 million Instagram users also use Twitter. Removing the ability of users to view Instagram photos directly through Twitter has them riled.

The photo-sharing service founded in 2010 by Stanford University alumni Kevin Systrom and Michel Krieger was purchased by Facebook Inc. (Nasdawq: FB) in April. The move suggests that Instagram seeks to draw some of Twitter’s traffic to its own very similar service.

Speaking last week at the LeWeb conference in Paris, Systrom said the decision to pull photo-viewing capability from Twitter was aimed at enlarging Instagram’s web presence.

“I think this is an evolution of just where we are, of where we want links to our content to go,” he said.

Instagram initially started its relationship with Twitter by providing just links. But then Twitter later integrated a service called Twitter Cards, which allows users to post multimedia content, such as links to YouTube video clips and photos.

Instagram’s business model is based on taking ordinary mobile phone images and processing them through filters to give them a retro look of square Polariod photos and then offers users a Twitter-like platform to post these images. However, using devices running Apple Inc.’s (Nasdaq: AAPL) iOS operating system and Google Inc.’s (Nasdaq: GOOG) Android operating system allows these photos to be viewed and shared.

Twitter and Facebook are the leaders in social networking. In September, the number of active accounts on Facebook topped 1 billion. Twitter announced earlier this year it had 500 million active accounts. Google Plus, which has been trying to gain market share by going head-to-head against Facebook by leveraging its immensely popular Gmail service, boasts about 235 million active users of its social networking service. MySpace, which was founded in 2003 and was once the leader in social networking service, had about 25 million active users in February.