Nearly 400,000 workers in Germany's metalworking and electrical sectors have joined strikes in the past week to push for higher wages, their union IG Metall said Wednesday.
On Wednesday alone 90,000 workers downed tools. Among the companies hit were BMW, Siemens and Bosch, with the southern state of Bavaria being the most affected.
"So far, more than 390,000 employees in 1,600 companies have participated in the warning strikes," said a statement by IG Metall, Europe's largest union with more than 2.2 million members.
The union is demanding a 5.5-percent salary rise this year for 3.7 million metalworkers spread across different branches, from automobiles to electronics. Employers have offered a 2.3-percent rise over a slightly different timeframe.
Several rounds of talks with the employers' federation, Gesamtmetall, in different states have so far failed to bring a deal, and the union has warned of stepped-up industrial action.
German "warning strikes", typically stoppages of a few hours, do not require a vote by members and are used to heighten pressure on employers during wage negotiations.
Pay talks in the metalworking sector are closely watched because they set the tone for other industries.