Social news pioneer Digg, facing intense competition from Yahoo's Buzz, has unveiled aggressive plans to grow in size and scope and boost its features.

Digg announced on Wednesday that it raised US$28.7 million in its latest funding round and that it will use the money to double its staff and expand internationally.

Digg, founded in 2004, popularized many so-called social news features, such as letting readers submit, vote for, rank and comment on articles, which have been adopted widely by mainstream news outlets across the Web.

Yahoo's recent launch of its social news site, called Buzz, has turned up the competitive heat in this space, and is likely a motivation behind Digg's improvement plans.

Digg, which said its traffic has doubled in the past year to around 30 million monthly unique visitors, has often been rumoured as an acquisition target by larger players like Google.

However, the company remains independent and, judging by Wednesday's announcement, up for the fight by, among other things, growing its staff from 75 to 150 employees by December of next year. Digg also plans to revamp its site's operation to make it easier for visitors to find content and customize their experience.

The company also intends to expand internationally, offer its service in other languages and improve its analytics tools for publishers. In addition, Digg wants to strengthen its advertising services to boost that revenue stream.

This latest funding round was led by Highland Capital Partners and also included Greylock Partners, Omidyar Network and SVB Capital. Digg previously raised $8.5 million in December 2006 and $2.8 million in October 2005.