Members of Germany's powerful IG Metall trade union launched warning strikes in the metalworking and electrical sectors in the early hours of Sunday, seeking better pay and job guarantees.
Around 300 employees of Thyssenkrupp's Rasselstein unit as well as workers from surrounding companies joined the first walkout at midnight, the union said.
The union has rejected an offer made by employers during a second round of wage negotiations, describing it as a "minus offer."
Employers have offered 1% of annual gross pay as a one-off payment in the summer of 2027 and an additional 1.3% increase from July 2028.
The union seeks a 5% pay raise over 12 months, as well as guarantees for jobs. The strike action at industrial sites is expected to spread across Germany next week.
IG Metall, Germany's largest union, aims to increase pressure during collective bargaining negotiations on behalf of approximately 3.7 million employees.
"The midnight warning strike at thyssenkrupp Rasselstein is merely the start of a massive phase of warning strikes," Jorg Kohlinger, head of IG Metall's central district, said.
The union said further warning strikes would follow in the coming days across the bargaining region covering the states of Hesse, Rhineland-Palatinate and Saarland as well as in Thuringia.
