Athletes at next year's London Olympics can blog and post comments on Twitter as long as it is not done for commercial purposes, the International Olympic Committee (IOC) has said.

But any found posting x-rated content could be booted from the Games, it warned.

In guidelines released by the Australian Olympic Committee (AOC) on Monday, the IOC "actively encourages and supports athletes ... to take part in 'social media' and to post, blog and tweet their experiences".

Bloggers and tweeters must, however, restrict themselves to "first-person, diary-type formats", must not report on events in the manner of journalists and must ensure their posts do not contain "vulgar or obscene words or images".

Dozens of athletes blogged during the last Olympics in Beijing in 2008, when Twitter was still a reasonably new phenomena, but the uploading of videos was banned and pictures restricted to prevent copyright infringements.

Still photographs taken at venues, largely banned in Beijing, may now be uploaded to social media sites but not sold or "otherwise" distributed.

The broadcast of video and audio taken inside the venues and the Olympic remains banned but athletes may post videos taken outside the venues.

The IOC gets much of its revenue from the sale of television and online media rights and is therefore highly protective of their intellectual property in that regard.