The July 5 Greek referendum on the debt draft deal with creditors will go ahead as planned, Greece's highest administrative court ruled on Friday.

The State Council was requested to examine the petition submitted by two citizens who questioned the legality of the referendum and asked that it be withdrawn.

Judges rejected the case over technical reasons and did not examine the essence of the objections as to whether the referendum was constitutional or not, Xinhua news agency report.

According to the argument of the two citizens, the referendum is unconstitutional, because Greece's constitution clearly states that referendums on fiscal matters are not allowed to take place.

In addition, they claimed that part of the question was not entirely clear to all voters and argued that the short notice does not allow citizens to be fully informed on the consequences of their choices.

Greek Prime Minister Alexis Tsipras's call for the referendum, as five month negotiations on the terms of a reforms for cash deal had hit an impasse, triggered dramatic developments in recent days that have fuelled fear that Greece was getting closer and closer to default and Grexit or exit from the eurozone.

With banks closed and capital controls introduced since Monday and with no financial aid from creditors, the Greek government has urged people to vote "No", arguing that this outcome would boost Greece's bargaining position from next week.

With Greece's banking association chief Louka Katseli admitting on Friday that ATMs will run out of cash on Monday, Greeks fear that "No" means that the banks would not reopen on Tuesday and the situation will deteriorate.

Opinion surveys show that Greeks are almost evenly divided heading to the referendum.