A loud explosion has been heard at Beijing Airport, according to Reuters. It might have just been a big package of gunpowder, though.
UPDATE: It was a homemade bomb, but the man only succeeded in injuring himself, according to the AP. Here's a photo from the moment the bomb exploded:
Photo said to be the moment the Beijing airport blast happened. Posted on Weibo (Chinese twitter). 1 man injured. pic.twitter.com/KpDN88zuaJ— Mark Stone (@Stone_SkyNews) July 20, 2013
UPDATE #2: Sky News has good video of what happened, so I've added a clip up top.