Greek unions planned protests in Athens and other cities on Thursday over the prospect of new austerity cuts demanded by the country's international creditors.
A small group of activists from the pro-Communist Pame trade union occupied the finance ministry in the early morning, taking down the EU flag and unfurling a massive banner.
"We have bled enough, we have paid enough," read the banner, which portrayed leftist Prime Minister Alexis Tsipras alongside his pro-reform predecessors, socialist George Papandreou and conservative Antonis Samaras.
Pame and civil servants' union Adedy were to hold protests in Athens, Thessaloniki and other cities in the evening amid reports that the government was nearing a new loan deal that includes fresh cuts.
Greek ministers are already preparing public opinion for 'temporary' tax hikes given the emergency situation.
"We must regrettably increase state revenue without new loans ... people must understand that these are temporary measures to help the recovery ... we will ensure that low-income Greeks will not be affected," Yiorgos Katrougalos, junior minister for administrative reform, told state broadcaster ERT.
Similarly, Economy Minister Yiorgos Stathakis told ERT there would be "a slight tax increase that will not affect low incomes."
Tsipras was to meet with Jean-Claude Juncker, chief of the European Commission, in Brussels Thursday after he agreed with the leaders of France and Germany to intensify efforts to conclude a bailout deal aimed at preventing Athens from going bankrupt.
The Greek premier's anti-austerity Syriza party won elections in January with a promise to ease the hardship caused by five years of austerity imposed under two international bailouts since 2010.
Unemployment climbed to 26.6 percent in the first quarter of the year, compared to 26.1 percent in the previous three-month period, the state statistics agency said Thursday.
An opinion poll published late Wednesday showed that 53 percent of Syriza voters favored breaking off the debt negotiations with the EU and IMF.
However, 50.2 of all respondents in the Marc poll for Alpha TV said they wanted the government to reach a deal with the creditors, and 80.3 percent said a deal was likely.
Greece's creditors have refused to release the last 7.2 billion euros ($8.1 billion) remaining in the country's EU-IMF bailout, which is due to expire on June 30, unless Athens agrees to tougher reforms.
Without the cash Greece will be unable to pay its foreign debts, after already ordering local authorities to hand over their cash reserves to meet earlier commitments.
A default could possibly send Greece crashing out of the euro.