Twitter marked the fifth anniversary of its public launch Friday with a slew of statistics demonstrating the explosive growth of the real-time blogging service.

"There were 224 Tweets sent on July 15, 2006. Today, users send that many Tweets in less than a tenth of a second," Twitter said in a message on its @TwitterGlobalPR account.

"Yesterday, we saw more than 600,000 signups. It took us more than 16 months to reach the first 600,000 Twitter accounts," Twitter said.

Twitter Engineering said it is delivering 350 billion tweets a day.

The San Francisco-based Twitter said last month that Twitter users are sending 200 million messages a day, most of which have to be delivered to multiple accounts.

Twitter co-founder Jack Dorsey fired off the first tweets on March 21, 2006 and the service opened to the public on July 15, 2006.

Twitter now has more than 200 million users.

According to a recent study by the Pew Research Center, 13 percent of online US adults use Twitter, up from eight percent in November 2010.