US President Barack Obama has won re-election, according to US TV network projections, while his Democratic Party looks set to retain control of the Senate, although the Republicans will continue to hold the House of Representatives.
Wild cheering broke out in Democratic campaign headquarters, with Obama himself expected to make a statement in Chicago.
The projections were made shortly after 5 a.m. but Republican challenger Mitt Romney conceded at 7 a.m. He said the US faced major challenges and he prayed that Obama would be successful in overcoming them. He urged Americans to come together and put the people before the politics.
He thanked his supporters, his wife and his vice-presidential nominee for their help.
President Obama made his acceptance speech at 7.40 a.m. as supporters cheered "Four more years".
He said the voters had reaffirmed the spirit which has triumphed over war and depression...'We rise or fall as one nation, one people.'
He said a decade of ar was ending and the economy was recovering and he was more determined than ever to improve the life of Americans. "You voted for action, not politics as usual, you elected us to focus on your jobs, not ours," he said, adding that he would focus on job creation, reducing dependence on oil and improving the tax system.
"For the United States of America, the best is still to come," he said. He too thanked his wife, telling her - 'Michelle, I have never loved you more'. He also thanked his children as well as vice-president Biden.
US elections are decided by the vote of the electoral college. Obama is so far projected to win 290 electoral college votes to Romney's 201. 270 guarantees victory.
Obama is also ahead in the popular vote, after having been trailing Romney for some time.
Obama scored victories in Wisconsin and Pennsylvania and was leading Romney in the battleground states of Ohio, Iowa, Virginia and Florida and Colorado.
At least 120 million people had been expected to render their judgement between the Democratic incumbent and Romney after a long, expensive and bitter presidential campaign that magnified the differences between Americans wanting to continue Obama's approach to fixing the ailing economy and those who want to try a new approach.
Television networks projected Romney the winner, as expected, in Republican states Alabama, Tennessee, Kentucky, West Virginia, Oklahoma, South Carolina and Indiana.
Obama was projected the winner in the Democratic strongholds of Maryland, Vermont, Connecticut, Delaware, Massachusetts and his home state of Illinois, as well as Washington, D.C. and California
CNN projected that Obama carried Maine.
Each man offered different policies to cure what ails America's weak economy, with Obama pledging to raise taxes on the wealthy and Romney offering across-the-board tax cuts as a way to ignite strong economic growth.
National opinion polls before the election showed Obama and Romney in a virtual dead heat, although Obama had a slight advantage in several vital swing states - most notably Ohio - that could give him the 270 electoral votes needed to win the state-by-state contest.
According to Reuters-Ipsos Election Day polling, one in three Obama voters said the economy was the most important issue for them, while half of Romney voters agreed. Healthcare was the second most important issue for Obama voters and the budget deficit was second for Romney voters. Unemployment was third for both.
Three-quarters of both Romney and Obama supporters decided to vote for their preferred candidate before the October debates between the candidates, according to the data.