Greek unions took to the streets Thursday to force the new government to change tack on its austerity polices as Prime Minister Lucas Papademos insisted he would press ahead with more spending cuts.

Papademos, in power since only 11 November , wrote to the EU and International Monetary Fund that his government would implement the tough measures agreed last month in a second bailout for debt-stricken Greece after a May 2010 rescue.

"The government will take all measures necessary in order to implement the (October accord) ... and achieve the objectives of the economic programme, which is crucial for improving the long-term welfare of the Greek people," he said.

Union leaders said people were fed up with spending cuts and higher taxes and warned they could seek common cause with groups in other countries.

Kostas Tsikrikas, head of the ADEDY civil servants union, said "workers continue their struggle against this unfair, barbarous policy ... We are going to coordinate our action with unions in other southern (eurozone) countries."

Tsikrikas conceded there were fewer protestors than at the last general strike 19 October  which attracted around 120,000 but added that "the problems are going to get worse, we have had enough and we can't go on like this."

Police put the demonstrators at 17,000 in Athens and 6,000 in the northern city of Thessaloniki as the sixth general strike this year shut down public services and crippled train and ferry services.

Flights, however, were not affected and the Athens stock exchange was open, as was most of the capital's metro system.

In central Athens, riot police were out in force around parliament as union posters of "No Austerity Budget!" hung from lamp-posts and a crowd of about 3,000 gathered in Syntagma square, scene of violent clashes in the past.

The protests follow similar strikes across Europe against spending cuts and tax increases introduced by governments fearful of getting sucked into the eurozone debt quagmire.

The protests were organised by ADEDY and the private-sector union GSEE whose chairman Yiannis Panagopoulos told AFP Wednesday that there "must be no illusions, austerity will continue in 2012 and so will our mobilisation because insecurity and the threat of unemployment persist."

Thursday's protest "is an expression of anger and exasperation directed both inside and outside the country," Panagopoulos said Thursday on Flash Radio, referring to resentment at perceived EU interference in the country's affairs.

Successive austerity packages have become tougher over the past two years as Athens has cut spending and hiked taxes in an effort to balance the public accounts, inflicting pain on many.

Passoula Vertzizoglou, 46, a university worker for 23 years, said she was protesting against short-time work and cuts in administrative staff, with her monthly salary now 700 dollars ($935), down from 1,150 dollars last year.

She said she now feared further staff cuts of up to 30 percent.

Other marchers, with similar personal stories, called for the government to concentrate on growth -- the Greek economy is mired in a deep recession -- rather than more austerity.

Rosina Kolonia, a retiree, said the government -- a technocratic administration formed only to implement the tough reforms tied to Greece's second bailout -- had no right to push the changes through.

"I am here because the government was not elected ... it can't commit itself nor commit the Greeks since it was not elected," Kolonia said, noting that her pension has been cut 25 percent since 2010.

"The spreading of the (eurozone debt) crisis shows that it is not the fault of the Greeks, it is the financial system that caused it," she added.

Papademos, a former European Central Bank vice president, heads a government which includes members of the opposition conservative and far-right nationalist parties who previously attacked the reforms agreed with the EU and IMF.

They have pledged, however, to support the measures which go to a vote -- and expected passage -- in parliament just before another eurozone debt crisis summit in Brussels on December 8-9.

GSEE and ADEDY, officially with a million members, have held more than a dozen general strikes against austerity plans in the past two years as Greece, saddled with a 350-billion-dollar debt mountain, struggles to keep its head above water.