At least 15,000 people including pensioners, teachers, doctors and lawyers, marched to parliament as lawmakers debated the new measures.
Despite pouring rain, crowds of protesters joined a rally late in the morning in Klafthmonos Square in the centre of Athens.
Without the agreement with its creditors, Greece faced the prospect of running out of cash to service its debts this summer, which could have seen it have another brush with bankruptcy. The left-led coalition government agreed to the reforms as part of a deal with the country's global creditors to release funds from its next bailout instalment. British Airways said it had retimed a number of its flights to avoid the strike period and put larger aircraft o some routes to and from Athens today.
Two men sail in a wooden boat next to moored ferries during a 48-hour nationwide strike of Greek seamen at the Port of Piraeus, near Athens, Greece May 16, 2017.
But another Athenian, Panagiotis Adamopoulos, disagreed.
"They told us they would end austerity and tear apart the bailouts", said Paraskevi Tsouparopoulou, 62. "If we dismiss it, surely we'll end up getting 300-euro ($330) salaries and 200-euro pensions".
In return, successive governments have imposed repeated waves of reforms, which have included steep tax hikes and salary and pension cuts.
The protest strike was called by the main public and private sector unions a day before parliament was due to vote on reforms that would unlock the next tranche of funds from an 86-billion-euro bailout. The government, which originally came to power in 2015 promising to repeal previous austerity measures, has vehemently rejected the accusation, emphasizing that it will also take other measures to relieve poverty.
Greece's creditors are still in disagreement over budget targets and the amount of debt relief needed to get the country back on a sustainable path.
Greece is now in the midst of its third bailout program the current three-year program expires in the summer of 2018 and could be worth up to 86 billion euros ($95 billion) in total.
While Greece's finances have improved under the rescue plans, the austerity has led to rise in poverty. And our promise to you is that we will always strive to provide indispensable journalism to our community.