Greece's biggest bank NBG reported a net loss of €537 million in the first quarter of 2012 as trading activities suffered and it was forced to set aside higher provisions.
National Bank of Greece (NBG) logged "losses of €537 million, due to the marked negative impact of trading income in Greece and the 47% increase (on an annual basis) in the group's provisions," it said in a statement.
Meanwhile, debt-stricken Greece is surviving on oil priced at a premium from trading houses Vitol and Glencore after EU sanctions against Iran.
Greece has been forced to halt Iranian oil purchases because of EU financial sanctions ahead of an oil embargo in effect from July 1.
The timing could hardly have been worse for Athens, which had become dependent on Iranian oil because most oil firms and banks would not extend it credit for fear it would default on its debts.
Trading sources told Reuters that Vitol and Glencore, the world's No.1 and 2 oil traders, have been supplying the bulk of the needs of Greece's top refiner Hellenic in the last two months.
Between them, the two firms have given Greece about €300 million in open credit financing, trading sources estimate, allowing Athens to keep buying oil without payment guarantees from banks.
Glencore has given credit for about €200 million, Vitol about €100 million, the trade sources said.
That has allowed Greece to avoid a steep slump in oil refining and escape fuel shortages.
But the rescue has come at a price because the trading houses are said by traders at rival companies to be charging a hefty risk premium.
Vitol and Glencore declined to comment on their roles in supplying Greece. Hellenic also declined to comment.
"It is all very complicated with Greece. Every deal is separate from the other, for every cargo you have different terms," a trader at one of the two trading houses said.
Because of their deep pockets and their willingness to take risk, Vitol and Glencore are the only firms that have been able to keep large quantities of oil flowing to Greece.
"If I had to deliver to Greece now, I would be feeling very uncomfortable," said a dealer at a Russian trading house who does not supply Greece.
Referring to the risk that the two firms are taking, he added: "An operational hole of $100 million would have killed me. But I guess Glencore or Vitol can afford having it. After all, the Greeks will manage to repay somehow in the future."
State Iraqi and Saudi oil companies continue to supply small amounts of crude to Greece and some companies, including Shell, continue sporadic shipments.
Iran had been offering generous credit terms to sell its oil amid tightening sanctions, and was willing to overlook Greece's debt problems and sell oil via "open credit" - an industry term meaning payments for oil can be delayed for 60-180 days.
The open credit system is risky as neither party has the support of a bank's letter of credit in case of non-payment.
Last year, Greece turned to Iran as its main supplier despite pressure from Washington and Brussels to end such trade as part of a campaign against Tehran's nuclear program.
Other European Union countries, including Spain and Italy, are phasing out Iranian imports because of sanctions, but none became as reliant on Iran as Greece.
Greek refiners relied on Iran for more than half of its oil imports during some months last year.
