Washington: US Democratic Party voters in Indonesia, where Barack Obama spent part of his childhood, have handed him a win over Hillary Clinton in the first voting abroad on "Super Tuesday," party officials said.

Seventy-five per cent of nearly 100 votes cast by expatriate Americans just past midnight went to Obama and 25 per cent went to Clinton, said Democrats Abroad officials in Indonesia.

Voting for Democrats living overseas have begun and will last until February 12.

Meanwhile, opinion polls gave Obama a 49 per cent lead over Clinton's 36 per cent in California.

Results still need formal verification.

"There is clear Obama momentum in California," pollster John Zogby said. "But in New Jersey, things seemed to swing in favor of Clinton, and Missouri was very mixed."

Obama had a 20-point edge in Georgia, aided by a more than 3-to-1 lead among black voters.