It said an initial 3,000 tickets – including 600 gymnastics tickets – were “put back into the pot” and sold on the London 2012 website on Sunday night.
More tickets returned by sports federations would be released the night before events, LOCOG added.
Transport chiefs say London’s morning rush hour went well on the first full working day of the Games.
Prime Minister David Cameron, meanwhile, said the empty seats were “disappointing” but not “a unique episode” with other previous Games facing similar problems.
At some venues, seats in the accredited “Olympic family” areas – reserved for groups including officials, sports federations, athletes, journalists and sponsors – have remained empty.
LOCOG communications director Jackie Brock-Doyle said organizers were doing everything they could to fix the problem.
“We’re doing this session by session, talking to the accredited groups – including obviously broadcast media and everybody else – and asking whether we can release, for the different sessions, tickets back into the public pot,” she said.
And she said accredited seating for London 2012 was down 15% on previous Games.
Lord Sebastian Coe – who has said Olympics venues are “stuffed” with sports fans – had earlier said that some empty seats would be filled by servicemen and women, as well as local students and teachers.
And shadow home secretary Yvette Cooper said unused tickets should also be given to police officers and their families.
Image source: Wikimedia Commons President-elect Donald Trump celebrated his election victory at the Ultimate Fighting…
Millions of voters across the US chose to return Donald Trump to the White House…
Donald Trump declares victory in the US election as he addresses jubilant supporters in Florida.…
Stocks around the world are rising as Donald Trump appears to be on the cusp…
Donald Trump has won Pennsylvania, North Carolina and Georgia and taken a lead over Kamala…
Quincy Jones, the celebrated musician and producer who worked with Michael Jackson, Frank Sinatra, Ray…