United States' President Barack Obama celebrated his victory over Republican rival Mitt Romney with the most popular Tweet of all time on the micro-blogging social network site Twitter.

After confirmation of his winning a second term in office as President, Obama simply wrote; "Four More Years", attaching this image of his embrace with his wife Michelle.



The message had an astounding 547,4221 retweets this morning, though the figure is still climbing. The tweet becomes the most-shared in Twitter's history, surpassing the previous record of 223,370 set by singer Justin Bieber (of perhaps slightly less gravitas).

There were more than 31 million election-related tweets on Tuesday night, and at the zenith of Obama's victory, 327,000 tweets-per-minute were being sent.  Election Night has been described as "the most tweeted about event in U.S. political history," by Twitter spokeswoman Rachael Horwitz.