ATHENS, July 3  -- A series of opinion surveys came to light on Friday in Greecewith pollsters underlining that the forthcoming Sunday's referendum over a debt deal with lenders was too close to call.

The "No" vote leads marginally by 43 percent versus a 42.5 percent for "Yes", in the poll conducted by Public Issue polling firm for Avghi (Dawn) newspaper.

However, when experts included respondents who initially said were undecided but were leaning more towards an answer, the result changed to 45.5 percent for "Yes" and 45 percent for "No".

According to the poll, 37 percent of respondents do not believe that "No" means a Grexit. Thirty-six percent of participants hold a diametrically different opinion and fear that "No" will lead to a return to the drachma.

Asked whether the responsibility for the failure to reach a deal after five months of talks lies with the Greek Leftist government or lenders, 41 percent of voters put the blame on creditors, 39 percent on the government and 15 percent on both sides.

The "No" vote prevails by 43 percent followed by "Yes" at 42.5 percent, according to another poll conducted by the University of Macedonia this week and released Friday.

According to this survey, four out of five Greeks want to keep Greece within the European common currency zone.

A third poll published on Friday in Ethnos (Nation) daily that was conducted by Alco polling firm saw "Yes" leading by 44.8 percent and "No" following with 43.4 percent.

The polling firm Pro Data noted that the "Yes" campaign gained momentum after the closure of banks and the introduction of capital controls on Monday.