The International Olympic Committee begins an investigation into claims Olympics representatives are selling thousands of London 2012 tickets on the black market.
The IOC's ruling executive board met over claims published in the Sunday Times involving more than 50 countries.
This included allegations that tickets for top events were available for up to 10 times their face value.
The IOC has referred the allegations to its independent ethics commission.
The UK's Olympics organiser, Locog, denied claims its chairman, Lord Coe, was persuaded to hand over extra tickets to an IOC national representative.
The IOC could also review how Olympic tickets are distributed among member countries - more than one million were distributed to those taking part in the Games.
The Games, which begin on July 21, will see the world's top athletes, including Usain Bolt (above) compete in and around London and the UK.
Thousands of the best seats at the top events - including the 100m final - were up for sale after being siphoned off from official supplies held by overseas national Olympic committees (NOCs), the newspaper said.
Countries whose ticket allocation is allegedly beeing sold on the black market include China, Serbia and Lithuania.
The Sunday Times alleges, during a two-month investigation in which reporters posed as Middle Eastern ticket touts, it found corruption involving people representing 54 separate countries.
Accusations include an allegation a member of the Greek Olympics Committee said he had "persuaded" Lord Coe, chairman of the London organising committee, Locog, to give Greece more tickets on the pretext demand had outstripped supply.
Locog denies the claim.
A spokeswoman said: "With regard to 'boasts' by the Greek Olympic Committee' (HOC) that discussions on tickets took place with Sebastian Coe, we can confirm this is untrue.
"Seb received a letter from the HOC (as he did from other NOCs) and responded saying that tickets had been allocated in accordance with the IOC's ticketing policy. There was no further contact - either formal or informal - on this subject."
More than one million London 2012 tickets were distributed abroad among all the nations taking part in the Games, but the IOC has strict rules to try to combat touts.
National Olympic committees must ensure that their allocation is only sold within their own region.
The IOC said in a statement on the latest claims: "The International Olympic Committee (IOC) has moved quickly to deal with allegations that some National Olympic Committees (NOC) and Authorised Ticket Resellers (ATR) have broken rules relating to the sale of Olympic tickets.
"The IOC takes these allegations very seriously and has immediately taken the first steps to investigate.
"Should any irregularities be proven, the organisation will deal with those involved in an appropriate manner.
London 2012 organising committee Locog said: "Rules and regulations for selling London 2012 tickets to international fans are clear and unambiguous.
"National Olympic Committees (NOCs) and their Authorised Ticket Sellers (ATRs) sign a contract with Locog agreeing to specific terms and conditions.
"The International Olympic Committee's (IOC) has launched an investigation in to the allegations and we will support them in any way we can. None of the tickets in question came from the allocation to the British public."