Greece was hit by a new wave of strikes beginning with teachers on Monday as public employees protested a massive redeployment plan ordered by its creditors in exchange for loans.
Around 7,000 public sector workers gathered from midday in Athens, according to police, grouping outside government ministries as riot squads kept a watchful eye on the crowds.
Isolated clashes broke out early in front of the ministry of administrative reform, the department coordinating many of the changes, with tear gas fired by police.
"No to extended leave, redundancies and mandatory transfers," read a sign tacked onto the closed door of a high school in Athens' well-to-do Kolonaki neighbourhood.
Students attended classes on a severely reduced schedule due to the strike launched by the education union OLME, and university staff will also force shutdowns at higher education establishments this week.
Savas Savas, president of OLME's Piraeus branch, said the government wanted "to end permanent jobs for public servants", and added the reforms "will lead to unemployment".
A spokesman for Greece's education ministry said that although high numbers were expected in the first few days of the strike the government was not counting on "sustained" walkouts.
OLME however has said strikes could continue into next week.
A mass strike of the entire public sector by its main general union is expected Tuesday and Wednesday.
As part of the controversial redeployment plan in the country reeling from six years of recession, civil servants have to accept new posts or spend eight months on reduced salaries as alternative posts are found, with the risk of losing their jobs altogether.
Staff in unemployment benefit offices will also leave them empty to join the protests, with hospital doctors joining the strikes from Tuesday to Friday.
The coalition government of conservative Antonis Samaras has agreed to redeploy 12,500 civil servants by the end of September as part of a general restructuring of its public sector, in return for the next instalment of its EU-IMF rescue loans.
All areas of the public sector must enter their share of staff into the redeployment plan and each department is defending its own workforce.
Overall, Greece is due to move or temporarily cut the salaries of a total of 25,000 civil servants and axe 4,000 state jobs by the end of the year.
The extent of protests is seen as a fresh test for Samaras, who boasts of stabilising Greece's economy and its periodic social unrest. Deputy Education Minister Simeon Kezikoglou on Sunday accused teachers unions of engaging in a political battle and taking students and schools hostage.
Alexis Tsipras, leader of the main left-wing opposition party Syriza, called on students and their parents to support the strikes and engage in "the great battle" of teachers.
Political analysts have speculated for weeks about the prospect of early elections, in which Syriza would take the lead according to recent polls.