Barack Obama easily captured Tuesday's North Carolina primary but narrowly lost to Democratic presidential rival Hillary Clinton in Indiana, the other key contest of the night.

Obama trumpeted the North Carolina win as a sign he'd rebounded after his ex-pastor Rev. Jeremiah Wright made racial comments that rocked the Illinois senator's campaign to become the Democratic presidential candidate.

Democratic presidential hopeful Sen. Barack Obama and his wife, Michelle, acknowledge supporters at a rally in Raleigh, N.C., on Tuesday night. (Jae C. Hong/Associated Press)"We've seen that it's possible to overcome the politics of division and the politics of distraction, that it's possible to overcome the same old negative attacks that are always about scoring points and never about solving our problems," Obama said to raucous cheering from his supporters in Raleigh, N.C.

"I love this country too much to see this country distracted and divided at this point in its history. I know the promise of America."

Obama said the win leaves him "less than 200 delegates away" from taking his party's presidential nomination.

With 99 per cent of North Carolina's 2,817 precincts reporting early Wednesday morning, tallies showed Obama took 56 per cent of the vote compared to Clinton's 42.

'Full speed on to the White House'

For much of the night, the Indiana race was too close to call, with Clinton leading by only a few percentage points.

But shortly after 1 a.m. ET, with all but one per cent of Indiana's precincts reporting, Clinton was projected the winner by the Associated Press, with 51 per cent of the vote compared to Obama's 49.

"Tonight we've come from behind, we've broken the tie and, thanks to you, it's full speed on to the White House," Clinton told supporters earlier in the night, referring to Obama's recent prediction that Indiana would signal the tiebreaker in race.

After four months of state contests, it will be nearly impossible for Clinton to overcome Obama's substantial overall lead in delegates and popular support by the time voting ends June 3.

But she's made it clear she's not giving up the fight and hopes to convince the superdelegates, who could decide the race, that she alone can beat Republican John McCain by capturing key swing states and lower-income white workers.

Tuesday's contests were the most important remaining primary elections in the Democratic party race to be the presidential nominee, and poll workers reported above-average turnouts in both states.

Obama widens lead

Democratic presidential hopeful Hillary Rodham Clinton offers a Sharpie pen to an aide after signing race car helmets while campaigning at the Indianapolis Motor Speedway earlier on Tuesday. (Elise Amendola/Associated Press)CBC's Neil MacDonald, covering the primaries from North Carolina, said Obama not only overwhelmingly took a high percentage of the black vote but also "a good share" of the white vote, despite Clinton's "strenuous efforts to deny him that."

"She had gone very populist here, posing as a beer-drinking, gun-loving, tax-cutting populist. She mocked Obama as an elitist," said MacDonald. "It didn't work."

Obama has widened his lead both in popular vote and in delegates, with only six smaller Democratic contests left before the primary season finishes.

Both candidates campaigned hard up to the last possible minute, flying between the two states to attend events and rallies on Monday.

They exchanged barbs over Clinton's promise to lift gas taxes to give American drivers temporary relief from soaring pump prices, and her threat to "obliterate" Iran if it attacked Israel with nuclear weapons.

Obama described that as irresponsible and said taking a few cents a gallon from gas prices wouldn't help anyone, but would damage an already indebted U.S. government.

But Obama's campaign has struggled in recent weeks following Wright's anti-American comments, which put their close to 20-year relationship in the media spotlight.

Voters in the two states, where the economy topped concerns, were divided evenly when asked whether the Wright controversy was a factor in their decisions.

The Illinois senator's biggest challenge remains wooing white blue-collar voters who have supported Clinton in recent contests.

274 delegates still up for grabs

Clinton's support among blacks in both states was down in single digits, according to exit polls, though she carried about 60 per cent of white votes in North Carolina and 61 per cent in Indiana.

Obama's chief strategist David Axelrod dismissed concerns about Obama's electability among white Democrats, saying they will fall behind him as the official nominee during the election.

Six smaller primaries with 274 delegates are still up for grabs, with the next contest in West Virginia on May 13.

The remaining contests are in Kentucky, Oregon, Puerto Rico, Montana and South Dakota before the party's August convention where so-called super delegates will have their say.

Indiana had 72 delegates at stake, while North Carolina had 115.

Obama began the day with 1,745.5 delegates, to 1,608 for Clinton, out of 2,025 needed for the nomination, according to the Associated Press.

Until Tuesday, Obama hadn't won a big state since Wisconsin in mid-February.

He faced criticism for comments he made about "bitter" small town residents and charges that he's an elitist out of touch with lower-income Americans.

With files from the Associated Press