Greece's main labor unions began a 24-hour general strike on Thursday, in protest against austerity measures imposed under Greece's international bailout. The strike, which is set to disrupt hospital, public transport, air traffic, tax offices and other activities, is the first major union action faced by the governing Syriza party, a left-wing movement that vowed to end austerity but that has had to accept Greece's creditors' demands to stay in the euro. The strike was organized by the country's two largest union groups, GSEE and ADEDY, which represent private and public sector workers respectively. GSEE said that it is against all belt-tightening measures that harm living standards in Greece. "The mass participation in the strike...will be our answer to the government's dogmatic obsession with dead-end and catastrophic policies that have squeezed employees and driven the youth of this country to lose all hope," GSEE said. Museums won't open on Thursday and hospitals and ambulances will run with skeleton staff. Employees at Greece's civil aviation authority are set to join the walkout, along with workers at the Metro underground and the country's ports. There will also be a media blackout due to the participation of journalists. Several marches will be held in the city centre by union groups that will finish at Syntagma square in front of parliament. Greece is currently locked in negotiations with representatives from its lenders, eurozone countries and the International Monetary Fund, in a bid to unlock EUR2 billion ($2.15 billion) of aid from its bailout. A key sticking point is over when banks would be able to confiscate homes from owners who have fallen behind on mortgage payments. Greece wants to prevent foreclosures on people on low-to-middle incomes living in properties valued at up EUR180,000, with higher thresholds for families with children. Greece's creditors are pushing for foreclosures to start on properties valued as low as EUR120,000, and with lower income limits. Talks between the two sides are scheduled to continue in Athens on Thursday. Eurozone peers have told Greece to implement a set of outstanding overhauls under its bailout program by the end of this week, in a process that will also pave the way to complete the recapitalization of Greek banks using eurozone bailout funds. Thursday's general strike is the first against the ruling coalition of left-wing Syriza and its right-wing junior partner Independent Greeks. The two parties swept to power in January elections and won re-election in snap polls in September. Syriza has been a harsh critic of austerity ever since the country signed up for its initial bailout in early 2010. But Syriza leader and Greek Prime Minister Alexis Tsipras was forced in July to agree to fresh fiscal retrenchment to head off a growing risk of the country exiting the euro. Despite the shift by the party and Mr. Tsipras, Syriza has issued a statement calling on its members to take part in Thursday's anti-austerity strike and march. Among the next batch of measures Greece will be submitting to parliament in coming weeks, as part of the required overhauls, are social-security reforms including the merger of pension funds and cuts to benefits. Farmers will also be hit with higher taxes. Both sets of measures that are likely to provide a major test for the government. More from MarketWatch