Hundreds of rioters plunged a peaceful demonstration in front of the Greek parliament in Athens into chaos on Sunday as lawmakers were debating the details of new bailout measures.
The rioters hurled Molotov cocktails and other objects at police. Broadcast footage showed police responding with teargas, with the acrid smoke spreading across Syntagma Square near parliament.
Through the day, thousands of people gathered in front of parliament to protest retirement benefit cuts and tax increases.
Police estimated that 20,000 people participated in peaceful protests. However, many of them fled the scene when the clashes erupted.
Lawmakers have been debating the details of a new bailout programme set for vote later Sunday, before eurozone finance ministers meet to discuss negotiations with the economically battered nation on Monday.
The savings package includes cuts to retirement benefits and income tax increases that should save 5.4 billion euros (6.2 billion dollars), a condition demanded by international creditors in order for the country to receive its next aid package.
Athens and its international creditors have struggled for months to agree on structural reforms and cost-cutting measures that would allow the cash-strapped government to continue receiving bailout aid. Concerns are growing that Greece is once again nearing the brink of bankruptcy.
European Commission President Jean-Claude Juncker said ahead of the finance ministers' meeting that he thinks Greece is on a good path.
"We're currently doing the first check of the programme, and the targets are as good as reached," he was quoted as saying in newspapers belonging to German publisher Funke Mediengruppe.
At Monday's meeting, finance ministers will "hold first discussions about how Greece's debt can become sustainable again," he said.
The vote was brought forward from Wednesday to strengthen the hand of Greek Finance Minister Euclid Tsakalotos in Monday's talks, according to government sources in Athens.
But the measures could be a tough sell in parliament, where the left-right coalition of Prime Minister Alexis Tsipras has a narrow majority of 153 lawmakers of an overall 300.
The austerity measures are a condition for the nation to receive a third aid package from international creditors, which has a volume of up to 86 billion euros.
The International Monetary Fund, one of the international creditors, has additionally urged eurozone governments to enter debt relief negotiations with Greece.
"For us the [law] is the gravestone of the retirement system as we know it," one protester said on Greek television.