Police and protesters clashed in Spain, Italy and Portugal as millions of workers went on strike in organised labour's biggest Europe-wide challenge to austerity policies since the eurozone debt crisis erupted three years ago.
Elsewhere, wealthier countries like Germany, the Netherlands and Denmark saw smaller, more peaceful displays.
Hundreds of flights were cancelled, schools were shut, factories were at a standstill and trains barely ran in Spain and Portugal. Stoppages in Belgium interrupted international rail services.
Protesters' anti-austerity message is supported by dreadful economic figures showing accelerating recession in southern Europe and big falls in manufacturing output.
All the focus, certainly in Brussels and Berlin, is on saving the Euro and avoiding the catastrophe that they think would follow a collapse of the currency.
But leaders in cities like Madrid have to see what their people are doing and saying. Much more of protests like today's, and this country could become ungovernable.
In Spain, where one in four of the workforce is jobless, 118 people were arrested - including two allegedly with material to make explosives - after confrontations at picket lines and damage to storefronts.
Riot police fired rubber bullets at protesters in central Madrid in one brief clash. Some 74 people were hurt.
Thousands took to the streets in Lisbon to mark the second general strike in Portugal in a year.
The action coincided with the announcement of new figures which showed GDP down 3.4 percent and unemployment up to 15.8 percent in the Iberian country, which is readying itself for a large tax hike.
In Rome, scuffles broke out between police in riot gear and demonstrators who threw stones, bottles and fireworks at police.
About 60 demonstrators were detained. Protesters occupied Pisa's mediaeval Leaning Tower for an hour, hanging a banner reading "Rise up. We are not paying for your crisis".