Germany's powerful metalworkers' union launched mass strikes Monday over pay and working hours, with some 15,000 workers putting down tools across the country, with 80 firms involved including car industry titan Volkswagen and its subsidiary Porsche, train manufacturer Bombardier and elevator maker Otis.
IG Metall also announced the names of 143 firms targeted for strikes Tuesday.
Up to 700,000 are expected to join a week of so-called "warning strikes", a familiar feature of the annual collective bargaining process that sees workers downing tools for a few hours to demonstrate at factory gates and in town squares.
IG Metall is asking for a pay rise of 6 percent, demanding that all workers have the option to temporarily switch to a 28-hour week. It also wants shift workers and those caring for children or elderly relatives to be compensated for some of the salary loss that would come with clocking up fewer hours.
"Workers aren't only workers, they have personal lives, children, old parents, all that must be taken into account. Working life can't only be about sacrifice," Berlin IG Metall chief Olivier Hoebel told hundreds of strikers demonstrating in the capital with bibs in the union's signature red color and whistles in hand.
The Gesamtmetall employers' federation has blasted the demands and any industrial action workers take to achieve them as outright "illegal", threatening to take the question to court.
If the two sides cannot agree on the negotiating terms negotiation at talks beginning January 18, the stage could be set for longer walkouts.
Boasting some 2.3 million members, IG Metall is Europe's largest trade union, representing workers of all kinds of industrial conglomerates like Siemens or ThyssenKrupp, steelmaking, the auto industry, electronics and textiles.