A Greek opposition leader has called on the prime minister to resign and led his party in a dramatic walkout during a parliamentary debate about the viability of the government.

Antonis Samaras' statements Thursday came amid an intense political crisis in Greece, after Prime Minister George Papandreou shocked the country and European leaders earlier this week by saying he wanted to put a hard-fought new European debt deal to a popular vote.

Samaras did not indicate whether he would vote in favor of the deal when it comes before parliament. But he stressed that he had said from the start that the latest agreement was "unavoidable."