Fast-growing micro-blogging service Twitter has reportedly raised an additional 35 million US dollars in funding and said Friday that it is ready to "begin building revenue-generating products."

Twitter co-founder Biz Stone, in a post on the company blog, said a new round of funding came from venture capitalists International Venture Partners and Benchmark.

Stone said Benchmark's Peter Fenton will join the board of directors of the San Francisco-based service that lets users share what they are doing at any given moment in brief text messages on computers or mobile telephones.

Twitter claims to have more than six million users.

"We weren't actively seeking more funding," Stone said. "Nevertheless, our strong growth attracted interest and we decided to accept a unique opportunity to make Twitter even stronger with a very attractive offer.

"Twitter is growing at a phenomenal rate," he added. "Active users have increased 900 percent in a year."

Stone did not provide a figure for the new funding round but several well-informed technology blogs put the amount at 35 million US dollars.

Twitter, which allows users to pepper one another with messages of 140 characters or less, has grown rapidly in popularity since it was launched in August 2006 but has been unable so far to generate revenue.

Stone said that would change.

"We are now positioned extremely well to support the accelerating growth of our service, further enable the robust ecosystem sprouting up around Twitter, and yes, to begin building revenue-generating products," he said.

Stone said Twitter's current workforce of 29 employees would expand.

"Throughout this year and beyond, our small team will grow much bigger to meet the challenges and opportunities ahead," he said.

"With these new partnerships and this new funding, we are in a position to move more confidently toward our vision for a robust and successful Twitter Inc," he added.