LONDON, Feb 29 (Reuters) - The world's top brewer Anheuser-Busch InBev on Thursday beat fourth-quarter sales estimates and raised its annual dividend by 9%, a move likely to cheer investors hungry for returns after years of focus on debt reduction.

AB InBev built itself into the world's largest brewer via a series of blockbuster acquisitions, which saw several major brewers internationally merged into one global giant.

But the acquisition spree also left the brewer with a debt overhang of more than $100 billion that it struggled to pay down as quickly as previously expected, limiting its ability to return cash to shareholders via dividends and buybacks.

AB InBev said in a statement that it had reduced its gross debt by a further $1.8 billion, to stand at $78.1 billion at the end of the year.

"As a result, we have additional flexibility in our capital allocation choices."

The decision comes after AB InBev announced a rare share buyback in October, boosting its shares.

The brewer also reported a 6.2% rise in fourth-quarter sales on Thursday, just ahead of analyst expectations of 6.1%, according to consensus estimates provided by the company.

(Reporting by Emma Rumney; Editing by Jacqueline Wong and Sherry Jacob-Phillips)