Greek schools shut, hospitals worked with emergency staff and train services ground to a halt on Thursday as unions held a 24-hour general strike to test the resolve of a new national unity government.

The strike is the first such test for new technocrat Prime Minister Lucas Papademos, who has had little time to celebrate since European leaders this week approved an 8 billion euro tranche of aid to prevent Greece from going bankrupt.

Unions representing about 2.5 million people -- around half of the national workforce -- called the strike to protest new austerity measures that are expected to heap more misery on Greeks already reeling from waves of salary cuts, layoffs and tax hikes.

The measures, part of Greece's 2012 budget due to be approved by parliament this month, come against a backdrop of rising anger and frustration over the austerity medicine prescribed by foreign lenders as the price for bailout loans.

Enough is enough. We have taken to the streets to say that this budget is an austerity budget -- a starvation budget -- which must not be passed, Christos Kiosis, a union chief at Athens water utility EYDAP told NET TV.

The 24-hour strike -- backed by two umbrella private and public sector unions -- is the latest in a long line of stoppages this year that have added to the debt-choked country's troubles. A 48-hour strike in October degenerated into violence with clashes between rival groups and police.

But Thursday's protest is expected to be smaller, with the sour public mood over austerity tempered by knowledge that elections are around the corner in February.

Shops and businesses in central Athens were open, but public services faced disruptions. Ships docked at Piraeus port, the country's largest, while trains, buses and trams halted morning service ahead of further stoppages in the evening. The ancient Acropolis site was shut to tourists.

Nothing has changed. It's the same policy. They have led us to the point of no return, said Panagiotis Proutzos, head of a Greek union for workers in the tourism sector. Greece is at a dead end and this is catastrophic for workers.

KILLING THE GREEK SPIRIT

Garbage collectors, doctors, journalists and bank employees were among others that walked off the job. Many schools stayed shut as teachers stayed home.

Rallies and marches are also due to be held during the day and thousands of demonstrators gathered in an Athens square.

They are killing us. They are killing workers. They are killing the Greek spirit, said Evangelos Routsas, 55. We are here to tell them we won't be silent.

Greeks like Routsas are complicating the task facing Papademos, undermining his efforts to reassure creditors that Greece will make the sacrifices it has promised.

In a letter to foreign lenders released late on Wednesday, Papademos said Greeks backed the reforms needed to secure its membership in the euro zone, adding that the government was determined to implement the measures.

Papademos' coalition has the express mandate to push through parliamentary approval of an unpopular 130-billion-euro bailout deal before polls pencilled in for February 19.

A former European Central Bank vice president, Papademos was sworn in last month after his predecessor, Socialist premier George Papandreou, was ousted over his call for a referendum on the bailout deal hammered out in October.

Since then Greece has tottered on the verge of bankruptcy, with squabbles among political leaders holding up the release of bailout money as European partners watched in exasperation.

With the aid tranche virtually secured -- it is expected to be released after International Monetary Fund approval next week -- Papademos' focus shifts now to pushing through parliamentary approval of the budget.

The package which includes tax hikes and spending cuts to bring the budget deficit down to 6.7 percent of GDP next year from 9 percent this year -- a task made more arduous by a deep recession now in its fourth year in Greece.

The country's central bank has warned of more pain ahead and has bluntly said the alternative to austerity is life outside the euro zone -- pushing the country back several decades.

(Writing by Deepa Babington; Editing by Ingrid Melander)