Greece's main opposition conservative New Democracy (ND) party leader and former Prime Minister Antonis Samaras resigned on Sunday evening after the updated official results of a critical referendum on the debt deal with creditors showed a strong lead of NO.Greek citizens turned down the offer for a reforms-for-cash deal international lenders made in late June with 61.5 percent of votes against 38.5 percent, with 71 percent of the votes counted, according to the Interior Ministry. Voters' participation reaches 61 percent.

The outcome could determine Greece's stay in the euro zone afloat or financial meltdown and Grexit should lenders interpret it as NO to Europe, officials and analysts in Greece and globally have noted.

Samaras who backed the YES took a share of responsibility for the results and announced that he is stepping down. Former Speaker of Parliament and ND heavyweight Vangelis Meimarakis was appointed as interim party chief.

All opposition parties have called on the Leftist government after the release of the first results to seek immediately a debt deal with lenders as soon as Monday to avoid plunging the country into bigger adventures.

Since July 1 Greece is already in arrears to the International Monetary Fund and without the safety net of the bailout program that kept it afloat over the past five years, is teetering on the brink of bankruptcy.

Since last Monday Greek banks are closed and capital controls have been imposed to avert the sector's collapse after the European emergency liquidity aid to the local banking system was cut off.

Greek officials have admitted that ATMS will run out of cash on Monday with no more financial support from creditors.

Proponents of the YES in Greece and analysts have warned that if the lenders will not "cooperate" as the Greek government expects in coming hours and a debt deal is not clinched, Sunday's NO may push Greece to disorderly default and jeopardize its membership in the euro with catastrophic consequences for the Greek economy and society.