Sept 10 (Reuters) - Investa Office Fund said it has set Sept. 17 as the date for its shareholders to vote on Blackstone Group's sweetened A$3.3 billion ($2.4 billion) bid.

Blackstone Group declared its A$5.52 per share offer as final.

The U.S. private equity giant increased its offer for the Sydney-focused landlord last week in response to a rival bid from Canada's Oxford Properties Group. (Reporting by Chandini Monnappa in Bengaluru; Editing by Stephen Coates)