Supporters of US President Barack Obama across the country and the world went literally wild after his reelection was confirmed on his Twitter and Facebook pages.

The posts came shortly after the major networks projected he would have a majority of electoral college votes.

Obama prevailed despite lingering dissatisfaction with the economy and a well-funded challenger in Mitt Romney, a former governor of Massachusetts.

With many states still reporting results, Mr Obama's margin of victory was not yet certain.

Obama's margin of victory is not yet certain because three states have yet to report results.

With swing states Virginia and Florida still too close to call, Obama has won 290 electoral votes to Romney's 203.

The state of Alaska, where polls have yet to close, is expected to vote for the Republican.