Protesters in Greece have forced their way into a government building in the country's latest anti-austerity protests, reaching just outside a minister's office before being forced out by police.

Police detained more than 30 protesters, including many union heads, on Wednesday, sparking clashes with about 200 demonstrators gathered outside the labour ministry in central Athens.

Police used pepper spray, batons and tear gas to in clashes with protestors.

The government said the demonstrators caused damage inside the building and threatened the minister, an accusation the protesters adamantly denied.

Greece has been gripped by a severe financial crisis since late 2009 and helped by billions of euros in rescue loans from other eurozone countries and the International Monetary Fund.

In response, the government has imposed waves of spending cuts and tax raises, leading to severe salary and pension cuts and leaving unemployment spiraling to above 26 percent.

Union members were protesting planned reforms to the pension and income contribution system, part of the latest spending cuts in the bailout program.

Other measures that took effect this year include a new 25 percent cut to the incomes of most public servants, leading to a string of new strikes and protests.

At least one protestor in Wednesday's demonstration was taken to hospital in an ambulance, while at least another two were treated by fellow protesters on the spot after collapsing, apparently from the effects of pepper spray.

Trading accusations

A ministry official said about 30 protesters made it into the labour ministry, breaking doors, overturning chairs and knocking files off tables.

They reached the waiting room outside the minister's office, where the minister, Yiannis Vroutsis, was present but unaffected.

"Violence in all its forms must be condemned, not only in words but also by actions,'' government spokesman Simos Kedikoglou said.

"The raid on the office of the labour minister, the material destruction and the threats against Yiannis Vroutsis are practices which aim to dynamite the political climate at a very critical time for the country.''

The protesters, however, insisted they were not to blame for any damage.

Dimos Koumbouris, head of a pensioners' union who was among those who entered the ministry on Wednesday, said union representatives had gone into the building seeking a meeting with Vroutsis.

Reached by telephone while still at police headquarters, where he said a total of 35 union heads and representatives were waiting to be charged, he said it was police who damaged the doors in their attempt to arrest the unionists.

"There was no damage. ... why would we do any damage?'' he told the AP, adding that they had wanted to meet the minister over social security reforms.

The minister himself issued a statement saying the demonstrators had tried to occupy the ministry, a common form of protest in Greece.

Strikes set to intensify

Strikes are set to intensify in coming days, with public transport workers and hospital doctors to hold a 24-hour strike in the capital on Thursday.

Port workers start a 48-hour strike the same day, leaving islands without ferry services. Other state-run services are also to be disrupted by work stoppages lasting several hours.

Last week, the government used emergency powers to force Athens subway workers to end rolling strikes that lasted eight days.

The Brussels-based European Trade Union Confederation strongly condemned the action taken by the conservative-led coalition government, noting that workers who defy civil mobilization orders face prison sentences of up to five years.

"The wheeling out of emergency powers to enforce austerity policies is unacceptable,'' ETUC general secretary Bernadette Segol said in a statement.

Farmers in central Greece angry at higher taxes and other austerity measures have been parking their tractors by central highways as their unions decide whether they will set up roadblocks.

Similar protests in the past have completely blocked the highways, essentially cutting the country in two.