Washington — US President Barack Obama has beaten his Republican challenger Mitt Romney to win a second term at the White House.
In a tweet to supporters, Obama wrote: "This happened because of you. Thank you," as crowds cheered in Chicago headquarters, ahead of his address to the nation.
Obama was projected to have won several key swing states, including Ohio, Pennsylvania, Wisconsin, Iowa, Nevada and New Hampshire, while Romney only won North Carolina. Florida and Virginia remained too close to call.
The relentless battle for the swing states gave Obama at least 290 electoral votes, while Romney just got 201 shortly after midnight.
Obama easily grabbed a host of "deep blue" states including California, Illinois and New Jersey, while Romney prevailed in "deep red" states of Texas, Kentucky and Georgia.
While Obama supporters had already started celebrations of his re-election, Romney conceded defeat.
In addition to the massive task of tackling US$1 trillion annual deficits and reducing a US$16 trillion national debt, Obama will have to deal with a divided US Congress that is likely to maintain the same partisan makeup in his second term in the White House.
The Election Day began with midnight voting in a pair of small towns in New Hampshire, and expanded across the nation after 5am. Voters lined up from New York to Florida to cast their ballots.
Early exit polls had shown 73 percent of voters were white, 13 percent were African American, 10 percent Latino and 3 percent Asian.