Micro-blogging service Twitter was taken offline for more than an hour on Thursday in what the company believes was a co-ordinated attack.

The popular site has been subject to a so-called denial-of-service attack, according to the firm's official blog. Denial-of-service attacks take various forms but often involve a company's servers being flooded with data in an effort to disable them. Facebook has also said it is "looking into" possible problems with its site.

More: http://news.bbc.co.uk/1/hi/technology/8188201.stm