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Microsoft co-founder Bill Gates has started tweeting.

The billionaire bid the Twitter community a "Hello World" around midday and then followed that message with three more lauding efforts to raise aid funds for earthquake-devastated Haiti, AFP reported.

The recently-retired Microsoft legend's Twitter page bore a blue check-mark icon used to verify identities of famous people using the popular microblogging service. Gates had signed on to "follow" messages at 40 other Twitter accounts, including those of Microsoft and its new Bing search engine.

Twitter users that Gates was tracking ranged from Queen Rania Al-Abdullah of Jordan and U.S. President Barack Obama to actress Ashley Tisdale and actor Ashton Kutcher.

"I'd like to welcome billgates to the twitterverse," tweeted Kutcher, who had 4,396,936 followers at the microblogging services as of late Tuesday. "Welcome to the club," tweeted U.S. television celebrity Ryan Seacrest of the popular American Idol program.

The number of people following him rose steadily as word of his arrival among the "twitterati" ricocheted with increasing speed in "retweets" through the day. Slightly more than 61,000 people had signed on to follow Gates towards the end of his opening day tweeting.

Twitter, fueled by smartphones and online bursts of 140 characters, soared to lofty heights in the past year and the number of users reportedly topped 40 million by the end of 2009. The company is said to have spurned takeover offers worth hundreds of millions of dollars from Google and Facebook.

In June, the U.S. State Department asked Twitter to delay scheduled maintenance on the service because it was being used by protesters angered by the results of Iran's disputed presidential election. More recently, Google and Microsoft began integrating Twitter messages into their respective search engines, a new feature described as real-time search.