Saudi Prince Alwaleed bin Talal, a nephew of the Saudi king, ranks 26th on Forbes' list of the world's richest people. (Stephanie McGehee/Reuters)

Saudi billionaire Prince Alwaleed bin Talal and his investment company said Monday they are investing a combined $300 million into Twitter, increasing the microblogging site's cash cushion as its user base expands.

Alwaleed's joint 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, and said the deal represents an interest "in promising, high-growth businesses with a global impact."

Twitter allows users to send short messages of up to 140 characters. 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 San Francisco-based 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 spokesman Matt Graves confirmed the investment but was unable to provide further details.

Alwaleed owns 95 per cent KHC, which has a major stakes in Citigroup Inc., Apple Inc. and Rupert Murdoch's News Corp.

Arab Spring boosts Twitter growth

His Twitter investment comes as Arab activists from Tunisia to Bahrain have flocked to Twitter to co-ordinate 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 one per cent of all Twitter messages, their volume has jumped 22 times over the past year, Semiocast said.

"Twitter is growing exponentially, especially in the context of the Middle East," said Ismail Patel, who follows digital media in the region for the research firm Informa Telecoms & Media. "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."

Alwaleed is launching a new Arabic news channel that will challenge established players such as Qatar's Al-Jazeera and Saudi-funded Al-Arabiya.

The channel, which will be called Alarab, is expected to begin operations next year and will feature reports from business news service Bloomberg LP. Alwaleed has said he hopes the new network will focus on the shifts taking place across the Arab world, with an emphasis on increased freedom of speech and of the press.

KHC also owns a sizable stake in a Saudi media company that produces the influential Arabic language newspaper Asharq al-Awsat and other publications.

Alwaleed's decision to buy into Twitter likely goes beyond his interest in media and technology.

Said Hirsh, a Mideast economist with Capital Economics in London, said rich Arab investors like Alwaleed have long targeted trophy assets and well established businesses.

"It is ... an investment into a well recognized brand with future growth potential," Hirsh said, adding that Twitter investors such as Alwaleed are unlikely to try to influence the user-generated content on the site. "I ... don't think that there is anything sinister behind it," he said.

Twitter recently began rolling out a series of tweaks designed to make the site easier to navigate. The redesign also aims to allow for more detailed information about corporate brands, as Twitter tries to convert more companies into advertisers.

The company earlier this year raised $400 million from venture capitalists and other investors. Twitter CEO Dick Costolo said in September that cash cushion would allow the company to control its own destiny — and for now avoid selling its stock through an initial public offering.

By limiting its shareholders to a small group of private investors, Twitter doesn't have to disclose how much revenue it brings in. The research firm eMarketer estimates Twitter will generate close to $140 million in ad revenue this year and $260 million in 2012.