By Padraic Halpin

DUBLIN (Reuters) - Flutter, the world's largest online betting company, nudged up its full-year guidance for the second successive quarter on Tuesday after its non-U.S. brands drove better-than-expected third-quarter revenue growth.

While Flutter's growth has been transformed by a gambling boom in the nascent U.S. market, where its FanDuel unit is the market leader, core profit at its more established brands in Britain, Europe and Australia jumped by 24% to $392 million in the quarter.

That helped push up total adjusted earnings before interest, tax, depreciation and amortisation 74% to $450 million, including a $58 million profit in the U.S., versus an investment-driven $55 million loss in the third quarter last year.

Third-quarter group revenue of $3.25 billion was well ahead of the $3.05 billion expected by 12 analysts polled by LSEG, and up 27% year-on-year.

"We've got just fantastic momentum across the ex-U.S. (business)," Flutter CEO Peter Jackson told Reuters.

Flutter raised its full-year adjusted EBITDA and revenue by 1% after a slight downgrade for Fanduel due to a run of customer friendly sports results so far this quarter that was more than offset by an upgrade everywhere else, which includes the Paddy Power, Betfair and Sportsbet brands.

It now sees 2024 core profit rising by 35% year-on-year and revenue by 22% at the midpoints of its forecast.

The Irish founded company said in September that it expects the booming U.S. market to account for almost half of an expected doubling of profit by 2027.

It said on Tuesday it has had a strong start to the key NFL season with peak wagers per minute already higher than during last year's Super Bowl.

Flutter announced plans for a $5 billion share buyback programme over the next 3 to 4 years in September, and said on Tuesday that it would commence the first $350 million tranche from this week.