Main opposition New Democracy leader Kyriakos Mitsotakis, speaking at the party's parliamentary group on Tuesday, lashed out at Prime Minister Alexis Tsipras.

"The main cause of the refugee crisis is the war, and they tend to forget it and put the blame on us," Foreign Minister Nikos Kotzias said in an interview with Skai TV late on Tuesday.

With up to 70,000 refugees expected to become stranded on Greece's northern border in the coming days, German chancellor Angela Merkel warned that the recently bailed-out Athens government could become paralysed by the huge numbers of arrivals from war-torn areas of the Middle East and Africa.