International Monetary Fund (IMF) Chief Economist Olivier Blanchard said on Thursday that Greece may need more debt relief and financing from its Eurozone creditors than estimated in IMF's report last week.

"We believe that current developments may well imply the need for even more financing, not least in support of the banks, and for even more debt relief," he said.

Blanchard warned that a Greek exit from the Eurozone would be "extremely costly" for Greece and its creditors.