The protest was against a newly passed law that requires the unemployed to seek jobs more actively or they will lose benefits.
By Friday, a civic initiative calling for cancellation of the law has amassed 140,000 signatures, making it the second popular initiative in Finland next to the marriage law initiative. According to Finnish regulations, a civic initiative has to be processed by the parliament if it has the support from at least 50,000 citizens.
Jarkko Eloranta, chairman of the leading blue collar central organization SAK, demanded that the implementation of the law be suspended until parliament processes the civic initiative in the coming spring.
The massive demonstration took place midday Friday at the senate square in Helsinki. The neoclassic square was filled with some 8,000 noisy demonstrators directing their protest to the nearby government building.
Among the traditional red flags of industrial and transport unions, there were also representatives of the academic sector. For example, the Union of University Teachers and Researchers joined the demonstration.
Researcher Janne Korhonen from the Aalto University Business School was carrying a placard saying "Use carrots, not sticks". He said to Xinhua that current economic policies endanger the society.
The mood in the square was tense. Organizers invited government party representatives to talk, but their voices were largely booed off.
Local commentators said the unions had accepted pay cuts in the 2016 agreement in return for a promise that unemployment benefits would not be further reduced. Now the unions claimed the cabinet had broken its promise.
Party chairmen of the Social Democratic Party, the Left League and the Green Party addressed the demonstration.
The Confederation of Industries said the all-day walk-out caused a loss of 120 million euros (149 million US dollars) to Finnish industries, but the union side claimed the correct figure would be 18 million euros.