Dockers at three big ports have staged protests at the requirement for all Italian workers to show a Covid pass.
The Green Pass shows whether you have had the Covid vaccine, recovered from it or had a negative test.
It became mandatory for all workplaces on Friday.
About 6,000 workers went on strike outside Trieste port, a maritime gateway for northern Italy, Germany, Austria and central Europe.
There was disruption in Genoa and Ancona too, but dockers worked normally in Italy's other major ports at Venice, Palermo, Naples and Gioia Tauro, Ansa news agency reported.
About three million Italian workers are estimated to be still unvaccinated and protests were reported in many of the big cities:
In Trieste, where only 40% of 950 port workers have had the jab, protesters chanted anti-government slogans as well as "No Green Pass"
Protesters blocked a key access road to Genoa's Sopraelevata road bridge, the main route from the centre to the west of the city
Strikes affected companies including Electrolux and San Benedetto
Two thousand people joined a demonstration in Bologna's central Piazza Maggiore
Hundreds of protesters occupied the Piazza Santa Maria Novella in central Florence
Similar numbers were reported in the Piazza Castello in Turin and a sit-in was planned at Rome's ancient Circus Maximus