Greek politician, Alexis Tsipras on Thursday said he will step down as leader of Greece's left-wing Syriza opposition party following a crushing defeat at the polls.

Voters handed New Democracy leader Kyriakos Mitsotakis an imposing election victory for the second time in five weeks on Sunday -- while Syriza saw a loss of tens of thousands of voters in just weeks.

The conservatives landed their widest winning margin in almost 50 years, with Mitsotakis securing a second term as Greece's prime minister.

"There are times when crucial decisions have to be taken," an emotional Tsipras told the press in Athens, saying he would call "elections within Syriza for a new leader, in which I will not be a candidate".

For many Greeks, former premier Tsipras is the prime minister who nearly crashed Greece out of the euro, and who reneged on a vow of abolishing austerity to sign the country on to more painful bailout terms.