With an unexpectedly severe pounding at the ballot box for leftist Syriza, Tsipras decided not to continue to a full term, which expires in October.

"I will request immediate declaration of national elections from the President of the Republic," Tsipras said. A party source said the earliest a vote could take place would be June 30, to allow for preparations.

Results for the European Parliament vote showed Syriza trailing the opposition New Democracy party by about nine points.

Syriza stormed the Greek political scene on an anti-austerity platform six years ago, then suffered a backlash after a third bailout in 2015.

More damagingly, there was a deeply unpopular agreement that resolved a long-running name dispute with North Macedonia.

New Democracy leader Kyriakos Mitsotakis demanded Tsipras resign, saying he had lost the popular mandate.

"The Prime Minister must assume his responsibilities. For the good of the country he must resign and the country should hold national elections, the soonest possible," Mitsotakis said.

Once a leftist firebrand, Tsipras, 44, mellowed after sweeping to power and telling the country's creditors to back off in 2015.

But he was forced into a painful new bailout months later, when faced with a choice of that or being turfed out of the Eurozone.

Greece emerged from close financial supervision in August 2018. The government this month introduced tax cuts and pension payouts, going some way toward unwinding some of the austerity measures.

Tsipras' decision to broker a deal ending a name dispute with North Macedonia earned kudos from European partners but was deeply unpopular with Greeks.

Coalition partner Panos Kammenos pulled out of the government in January, triggering a confidence vote in parliament that Tsipras nonetheless won.

For most, use of the Macedonia name is an appropriation of Greek heritage by the country's neighbour. Regardless, Tsipras signed the name-change deal.

Australian Associated Press