Greek doctors, prison staff and other state workers went on strike this morning to protest against public sector job cuts imposed as part of the country's €240bn international bailout.
The 24-hour strike, which is expected to culminate with a midday rally before parliament, coincided with the start of a visit to Athens by inspectors from the Troika.
The international lenders, the International Monetary Fund, the European Union and European Central Bank, have demanded austerity measures.
"At a time when the government steps up its attack against workers, our response will be strong," said public sector union ADEDY in a statement on the strike, which has led to hospital shaving to draft in emergency staff.
Greek labour unions have fiercely resisted government plans to shrink the 600,000-strong civil service through layoffs or transfers of workers.
They fear the measures will further worsen the plight of Greeks struggling through a six-year recession.
The finance and administrative reform ministries filed a lawsuit against the strike and a court ruling is expected later today.
While Greece is beginning to emerge from its protracted recession, anti-austerity sentiment remains high in the country, where repeated rounds of spending cuts and tax hikes since its rescue from bankruptcy in 2010 have driven up unemployment and homelessness and eroded living standards.
Last week, Greece suffered brief power outages due to a strike by electricity workers protesting against plans to sell off part of its biggest power producer, Public Power Corp, to a private competitor in 2015.
The government took legal action and forced the strikers back to work on Saturday.
It is eager to avoid major disruption during the summer holiday season as tourism is central to Greece's hopes for economic recovery.
PPC's biggest trade union GENOP-DEH, Greece's private sector union GSEE and the Communist-affiliated trade union PAME will stage a demonstration outside parliament later today as politicians inside debate a draft bill on the PPC privatisation.
"Electricity is a public good, not a commodity to be sold off cheap, and those who do so must be held accountable to society," GSEE said in a statement.
"The fight against the privatization of PPC is a long one and it will not end even after the bill in question is passed."
The Troika inspectors, who are in Athens to check on Greece's progress under the bailout programme, are due to meet newly-appointed Finance Minister Gikas Hardouvelis tomorrow.