They claimed 58% of available tickets for the first session were sold, and 65% for the evening session.
Ticket prices and VIPs not filling their allocations have been cited as reasons for empty seats.
"Without heroes and local athletes the public take longer to fall in love," said Rio 2016 spokesman Mario Andrada.
"But one of the legacies of the Games will be to show Brazilians how spectacular these other sports can be and there will be no problem when Usain Bolt competes on Sunday."
