Saudi billionaire Prince Alwaleed bin Talal has doubled his stake in Twitter, now owning more than 5 percent of its shares, which are worth approximately $1 billion, according to CNET.

Alwaleed acquired a 3 percent stake in 2011 and spent about $50 million to increase his share to his current 5 percent. He now owns approximately 35 million shares when including those owned by his investment arm, Kingdom Holding Company. This combined holding makes him Twitter's second-biggest shareholder behind co-founder Ev Williams and ahead of CEO Jack Dorsey.

Although Alwaleed's share increase is seen as an endorsement of new Twitter CEO Jack Dorsey by many, his comments on Dorsey in June make this uncertain, according to Quartz. Furthermore, Alwaleed is not the only investor that has voiced concerns over Dorsey due to his involvement in his other company, Square.

"Jack has another company called Square which requires a lot of attention and a full-time job round there," said Alwaleed. "I believe and trust that Jack Dorsey is there on a temporary basis."

Despite Alwaleed's high investment in Twitter, he does not use the social media platform regularly, with just 171 tweets since he set up his account in 2013, according to Forbes.

Alaweed also owns shares in various other companies including Citigroup, News Corp and Four Seasons Hotels and Resorts.