The Times writes,
In an elaborate payment system that began after the May 6 election that brought down the Greek government and is meant to ensure that the Greeks do not touch the cash, the big three creditors - ECB, IMF, and EC - are now wiring bailout payments to an escrow account in Greece. There the money sits for two or three days - before much of it is sent back to the troika as interest payments on the Greek bonds that Europe accepted under terms of the bailout deal struck in February. About three-quarters of Greece’s debt, or $229 billion, is now effectively owned by one of the three troika members, according to estimates by the investment bank UBS...
Early this year, Greece forced a 75% haircut on its private creditors in return for its banks being eligible for cheap credit from the ECB's Longer term refinancing operation (LTRO). After this, most of Greek public debt is in the form of loans from EU, IMF and the EFSF (such lending is either directly to governments or by purchase of government bonds from the secondary market) and Greek government bonds held by the ECB.The European authorities are effectively lending Greece money so Greece can repay the money it borrowed from them... Since May 2010, Greece has been sent about $177 billion in European taxpayer money to keep the country afloat and ward off a bigger crisis that might threaten the entire currency union. Of that amount, a full two-thirds has gone to pay off bondholders and the troika. Only a third has been earmarked to finance government operations, with only a tiny sliver spent on stimulus projects for the anemic economy.
See also this overview of Europe's public debt cross-holdings.