DUBAI, United Arab Emirates – A Saudi billionaire and his investment company said Monday they are investing a combined $300 million in Twitter, increasing the microblogging site’s cash cushion as its user base expands.

Prince Alwaleed bin Talal’s investment with his Kingdom Holding Co. follows months of negotiations and will give them a “strategic stake” in Twitter, according to the Riyadh, Saudi Arabia-based investment firm. It wasn’t clear how much of Twitter the prince will control.

Alwaleed, a nephew of the Saudi king, ranks 26th on Forbes’ list of the world’s richest people. He has a history of investing in media and technology companies.

The San Francisco-based company lets its users send 140-character messages. The five-year-old site has been instrumental in connecting protesters and relaying on-the-ground developments during this year’s Arab Spring uprisings.

Globally, the company has more than 100 million active users who post an average of 250 million messages, or “tweets,” a day.

“We believe that social media will fundamentally change the media industry landscape in the coming years,” Ahmed Halawani, KHC’s executive director of private equity and international investments, said in a statement. “Twitter will capture and monetize this positive trend.”

Twitter is revamping the site to make it faster and simpler to navigate. The company may boost ad revenue by 86 percent next year as it attracts more international advertisers, according to EMarketer Inc.

Alwaleed’s investment comes as Facebook, the most-popular social networking site with more than 800 million users, is said to consider raising about $10 billion from an initial public offering.

Twitter confirmed the investment in an email, declining to give additional comments.

Alwaleed owns 95 percent of KHC, which has major stakes in Citigroup Inc., Apple Inc. and Rupert Murdoch’s News Corp.

Arab activists from Tunisia to Bahrain have flocked to Twitter this year to coordinate protests and voice their opposition to long-ruling autocratic regimes.

Arabic is now the fastest-growing language on Twitter, according to a study released last month by French social media research firm Semiocast.

Although Arabic tweets account for just over 1 percent of all Twitter messages, their volume has jumped 22 times over the past year, Semiocast said.

“The Middle East is an important region for Twitter. And Twitter is becoming increasingly important for all Middle East residents … because of the Arab Spring protests,” said Ismail Patel, who follows digital media in the region for the research firm Informa Telecoms & Media.

– Bloomberg News contributed to this report.