Two of Australia's largest bookmakers are refusing to pay out on bets that Barack Obama would win the U.S. presidential election, citing fears he could be assassinated before his inauguration, a report said Saturday.

The two bookmakers, Sportsbet and Centrebet, told the Sydney Morning Herald they would not pay out on the bets until the first African-American U.S. president takes office in January.

A spokesman for Centrebet told the paper it was a matter of policy.

The Herald said its story was prompted by a punter who said a senior official at Sportsbet had refused to pay out on a bet citing assassination fears.

Sportsbet chief executive Matt Tripp denied this was the company's main concern.

"God forbid he has a stroke or gets hit by a bus," Tripp told the paper. "I love the bloke. I want to pay out on him. I think he is good for America and good for the world."

Bullet-proof screens were put up on stage when Obama made his victory speech to jubilant supporters in a Chicago park.

Two white supremacist skinheads were arrested in the U.S. state of Tennessee in October over plans shoot Obama, although the plot appeared unsophisticated.

Irish bookmaker Paddy Power was so sure of the election outcome that it paid out Obama-backers in October.

Other Australian bookmakers have paid out on Obama's victory, the Herald said.