Opposition leader Alexis Tsipras on Monday hailed Parliament's failure to elect a new head of state as a "historical day" in a brief address outside Parliament after lawmakers voted against the coalition government's presidential candidate, leading Greece to early elections.

"Greek lawmakers, the parties of the democratic opposition, proved that democracy cannot be blackmailed despite the pressures and machinations," the SYRIZA chief said.

"When the large majority of the Greek people is determined to put and end to the policies of the memorandums and austerity, then deputies can do nothing more than respond to their duty and act in accordance with the will of the people," Tsipras said.

"The future has already started, be optimistic and happy about that," he said.