An elderly man is crying outside a national bank branch as pensioners queue to get their pensions, with a limit of 120 euros, in Thessaloniki Friday. Greece is almost evenly split over a crucial weekend referendum that could decide its financial fate, with a "Yes" result possibly ahead by a whisker, the latest survey Friday showed. Photo: AFP

Greece was officially declared in default on Friday, injecting even more urgency into a make-or-break weekend referendum that new polls suggested was too close to call.

The fund providing Greece's financial lifeline declared "an event of default by Greece."

The European Financial Stability Facility added, though, that it had decided to not immediately demand repayment of its loans - a step that analysts say could have triggered a sudden "Grexit," or Greece's exit from the eurozone.

The news will come as a fresh shock to Greece's 11 million people, and will hang over two major, rival rallies taking place in Athens late Friday seeking to galvanize "Yes" and "No" support for Sunday's referendum.

Greek Prime Minister Alexis Tsipras on Friday said an IMF analysis showing Greece's debt is unsustainable justifies his government's decision to reject an aid package from creditors that offered no debt relief.

In a televised address to the nation on the final day of campaigning ahead of Sunday's referendum, Tsipras renewed his appeal to Greeks to vote against the bailout package and say no to blackmail and ultimatums.

"Yesterday an event of major political importance happened," Tsipras said. "The IMF published a report on Greece's economy which is a great vindication for the Greek government as it confirms the obvious - that Greek debt is not sustainable."

Tsipras called for "a 30 percent haircut off the Greek debt" and "a 20-year grace period" for the rest, to ensure "the viability of debt" in Greece, which currently stands at nearly 180 percent of its gross domestic product (GDP).

However, Greece's negotiating position with creditors would be "dramatically weakened" in the event of a "No" vote in Sunday's bailout referendum, European Commission chief Jean-Claude Juncker said Friday. He added that even if the 'Yes' vote wins, there would still be "difficult" negotiations ahead.

Rival camps in Greece are set to hold major rallies in Athens ahead of Sunday's crucial referendum and both sides are now racing to reach voters before time runs out, with "Yes" and "No" posters vying for space, BBC news reported.

A poll published in Greece's Ethnos newspaper on Friday showed the two sides evenly split, with the "Yes" vote at 44.8 percent and the "No" vote at 43.4 percent.