Protesters have gathered outside parliament in Greece ahead of a vote on further austerity measures in return for more international bailout money.
The rally coincides with a three-day general strike against the introduction of tax and pension changes.
Greece has been unable to unlock the next loan instalment of €5bn (£4bn) after clashing with its creditors over the need for more reforms.
The protests come amid fears of another crisis in the Eurozone.
An extraordinary meeting of the Eurogroup is being held on Monday.
Greece agreed to a third rescue package worth €86bn (£60bn; $94bn) last year.
There are worries it may default on €3.5bn in debt payments due in July if an agreement is not reached soon.
The International Monetary Fund and other European partners are demanding that Greece implement further austerity measures to generate nearly €4bn in additional savings – contingency money in case Greece misses future budget targets.
Eurogroup ministers from countries which use the euro will assess “a comprehensive package of policy reforms as well as the sustainability of Greece’s public debt”, a statement says.
“Both elements need to be in place in order to finalise the programme’s first review and unlock further financial assistance to Greece.”
At the scene: Yogita Limaye, BBC News, Syntagma Square
Once again protesters have gathered in Syntagma Square, just outside Greece’s parliament, as lawmakers debate tax and pensions reforms inside the building. Thousands marched in Athens on Saturday – but Sunday’s rally is expected to be even bigger.
The changes expected to be approved by MPs include tax hikes and pension cuts, which naturally have a lot of people here worried.
A man who runs a meat stall at Athens’ main market told me that if the bills went through, he would simply stop paying up, because for him it would mean a choice between his children going hungry and paying taxes.
But some do support the government. A taxi driver I met said he thought Prime Minister Alexis Tsipras was a strong leader and he understood that difficult decisions were necessary to pull the country out of the financial crisis.
Nail in the coffin
Unions have said the proposed overhaul of the pensions system and rises in social security contributions are designed to win favour with eurozone finance ministers.
Greece’s largest labour union, the private sector GSEE, said the changes, were the “last nail in the coffin” for workers and pensioners.
The nationwide strikes are the fourth series to be called since Prime Minister Alexis Tsipras’s government won re-election after organising a referendum on the country’s bailout.
Mr Tsipras was elected initially on an anti-austerity ticket but later signed up to Greece’s third international bailout since 2010. He has a thin majority with 153 MPs in the 300-seat parliament.
Last summer, the crisis peaked when Athens defaulted on its debt payments and raised the spectre of an exit from the eurozone.
Greece is already looking to implement spending cuts that will amount to 3% of the country’s gross domestic product or €5.4bn euros by 2018.