The leader of Greece's Syriza party has vowed to end the country's "national humiliation" as opinion polls show the party's lead is widening ahead of Sunday's election.

Alexis Tsipras told thousands gathered in Athens that an outright victory for the leftist party would allow Greece to turn its back on four years of austerity.

"On Monday, national humiliation will be over. We will finish with orders from abroad," Mr Tsipras told the election rally. "We are asking for a first chance for Syriza. It might be the last chance for Greece."

The Syriza party's platform of pledging to overturn austerity cuts and demand European debt write-offs has unnerved financial markets.

However, many in Greece have embraced the party's promises as the country struggles with unemployment of more than 25% and pension cuts.

During the rally, Mr Tsipras was joined on stage by Pablo Iglesias Turrion, the leader of Spanish left-wing party Podemos.

Supporters waved Greek flags and placards reading "Change Greece, change Europe".

Opinion polls released on Thursday showed that Syriza has widened its lead over Prime Minister Antonis Samaras' conservatives. Mr Samaras is due to hold his final election rally today.

A poll by Metron Analysis suggests Syriza's lead over the New Democracy party has grown to 5.3 points, up from 4.6 points.

Syriza could claim as much as 36% of the vote, putting it on the verge of an outright victory, according to the poll.

Analysts fear a victory for Syriza could lead to confrontations with the European Union and the International Monetary Fund, and a possible Greek exit from the Eurozone.

Under Greek electoral law, parties must secure 3% of the vote to enter the 300-seat parliament, with the largest party claiming a 50-seat bonus.