A Greek public prosecutor on Monday charged power workers for occupying a public utility building in an anti-austerity protest broken up by police ahead of a visit by German Chancellor Angela Merkel.
Police stormed the building late on Sunday and arrested 18 members of Greece's powerful GENOP union after workers took over a data centre of the state-controlled utility PPC and unfurled a banner reading "We resist".
"No matter how many times they arrest us we will not bow our heads," GENOP leader Nikos Fotopoulos told reporters after leaving the prosecutor's office on Monday.
All 18 were charged with disturbing the peace and face up to a few months in prison if convicted. They were released pending trial, court officials said.
GENOP, one of Greece's most militant labour unions, has promised action against a new wave of belt-tightening demanded by the country's international lenders, including rolling 48-hour power strikes when austerity measures go to parliament.
Sunday's occupation was part of protests against a deeply unpopular property tax collected through electricity bills that was imposed last year to shore up the country's finances. The union also opposes planned wage cuts and layoffs.
Police in full riot gear entered the building and forcibly evicted the unionists, who shouted anti-government slogans, the latest in a series of clashes with protesters.
Greek Prime Minister Antonis Samaras promised on Thursday to maintain law and order after unpaid dock workers stormed the defence ministry.
"I will not allow this country to become defenceless," he told reporters.
Discontent with EU/IMF-imposed budget and wage cuts is rising in Greece. Merkel is due to visit Athens on Tuesday in an intended show of support for the austerity policies pursued by Samaras' fragile three-party ruling coalition.
But she faces a hostile reception from a people worn down by years of recession. Demonstrations are planned in the Greek capital. Many Greeks blame Merkel and the austerity policies she is backing across Europe for their plight.
The Greek economy has shrunk by about a fifth since 2008, partly due to austerity measures demanded in exchange for the bailouts. Unemployment in the private sector is at a record 24 percent. State workers have lost about a third of their income.