They were taking part in their fourth general strike this year – and the first since three people died when a bank was torched.
Two separate rallies ended peacefully, but shopkeepers had taken extensive precautions in case the protests turned violent, as did the one two weeks ago.
Store owners closed up and lowered protective shutters before the march got underway, and police deployed 1,700 officers and detained 36 people in an early show of force.
Demonstrators outside the parliament building banged pots and pans and shouted “Thieves, thieves!” but did not attempt to breach a cordon of riot police holding them back.
The strike closed schools, halted ferries and trains, and left hospitals running with only emergency staff. The Acropolis and other ancient sites in Athens were also shut.
Premier George Papandreou, visiting Lebanon, said he sympathized with many of the protesters.
Unions are protesting harsh measures imposed by the cash-strapped government. During Greece’s last general strike on May 5, three workers – including a pregnant woman – died when a bank was torched by rioters.
Protesters observed a minute of silence for the three victims before today’s march.
Public anger has grown at deep pension and salary cuts, as well as steep tax rises, imposed in an attempt to pull Greece out of an unprecedented debt crisis. The measures were needed for Greece to receive a €110bn three-year rescue loan package from other EU countries and the International Monetary Fund that staved off bankruptcy.
Ilias Iliopoulos, general secretary of Greece’s public servants’ union, Adedi, said low-income workers were being burdened unfairly.
Earlier, members of a communist-backed union occupied the Labor Ministry and held a separate peaceful rally.
About 5,000 protesters also marched in Thessaloniki, Greece’s second-largest city.
The country’s debt crisis has sent shock waves through global markets. That, combined with fears for Europe’s struggling economy and German warnings that the future of the euro is at stake, sent the common currency to a four-year low against the dollar yesterday.