The anger of the trade unionists in Greece have stormed the ministry of employment and face the minister plans to tighten the rules on strikes.
About 500 protesters from the Communist-affiliated PAME arrived in the department after breaking open the metal shutters with crowbars, the Reuters news agency has reported.
They shouted “shame on you!” and “take it back!”, left-wing minister, Effie Achtsioglou.
Curbs on strikes are among the conditions for Greece to exit its bailout.
The left-wing government of Prime Minister Alexis Tsipras has submitted a huge bill in the parliament to satisfy the creditors of the euro zone, who have demanded austerity in exchange for further loans to Greece.
Reality check: the Greek bailouts worked?
Greece in first bond sale for three years
Greek man arrested over letter bombs sent to EU officials
Among the proposed reforms is a rule requiring unions to get a yes to at least half of their members before a strike. Currently, the approval of one-third of the members is required.
In the time of the confrontation on Tuesday, the unionists have appealed to the minister of labour to withdraw the legislation.
But Ms. Achtsioglou replied: “I’m not going back.”
The protesters chanted “We will not bow to the plutocracy!”
The government of Tsipras wants to avoid another bailout programme after the current one – the third – expires on 20 August.
The austerity imposed by the european UNION and the International Monetary Fund (IMF) creditors has caused enormous suffering for millions of Greeks, after spending on social security, education and health has been drastically reduced.
Burdened by colossal state debts, Greece has been a lifesaver for economic since 2010. It has received more than â‚¬250bn (Â£221bn; $298bn) in the rescue plan payments.