Greeks voted Sunday for the second time in six weeks in what was arguably their country's most critical election in 40 years, with the country's treasured place within the European Union's joint currency in the balance.

The political turmoil sparked by a two-year financial crisis has roiled markets across the world, with fears that victory by parties that have vowed to cancel the country's international bailout agreements and accompanying austerity measures could see Greece forced out of the euro.

That in turn would likely drag down other financially troubled countries and rip apart the euro itself.

The last opinion polls published before a two-week pre-election ban showed the radical left Syriza party of Alexis Tsipras running neck-and-neck with the conservative New Democracy party of Antonis Samaras. But no party is likely to win enough votes to form a government on its own, meaning a coalition will have to be formed to avoid yet another election.