ATHENS Greece's Alexis Tsipras stepped down from the helm of the leftist Syriza party on Thursday following a heavy election defeat.

"The time has come to start a new cycle," Tsipras said in a televised address, adding that a reform of the party was necessary.

Led by Tsipras, Syriza stormed to power in 2015, at the height of Greece's deep economic crisis, riding a wave of anti-austerity and anti-bailout anger among Greeks.

It lost to Prime Minister Kyriakos Mitsotakis's New Democracy in 2019.

In Sunday's vote, Syriza won just 17.8% of the votes, against 40.5 for New Democracy.

"The negative result can - and must - become the beginning of this cycle," he said.

Tsipras said he was stepping down to pave the way for elections for a new party leader, saying he would not be a candidate.

"I am proud of everything that happened," he said.

"This difficult journey had compromises, and difficult decisions, and injuries and attrition, but it was a journey that left a mark on history."

(Reporting by Renee Maltezou, Karolina Tagaris, Angeliki Koutantou and Lefteris Papadimas; Editing by Toby Chopra)