Greek conservative leader Antonis Samaras on Friday said a government after indecisive weekend elections cannot be formed without the radical left Syriza party that opposes the EU-IMF loan agreement, AFP reports.

"There must be a durable government," Antonis Samaras told his New Democracy party deputies. "The Syriza party must participate, or give a vote of tolerance. It's in their hands to decide what they want to do," he said.

The Greek ballot on Sunday, which delivered a strong anti-austerity message, has alarmed the country's European peers which fear that vital reforms may be now at risk.

Even mainstream parties have publicly called for a revision of Greece's EU-IMF loan agreement which international creditors are unlikely to accept.

Samaras on Friday repeated his assertion that the loan agreement must be "modified" to boost growth in a country mired in a five-year recession.

"We have asked for changes to measures that have caused incredible recession," he said. "One after another, European leaders are also asking for changes."

The European Union has warned that Greece must honor the bailout conditions of budget cuts and deep reforms.