The powerful German union IG Metall organized a series of warning strikes overnight, hitting the automobile sector in particular, to turn up heat in wage negotiations for around 3.4 million metal sector workers across the country.
A truce period during which unions are not allowed to stage any industrial action ended at midnight and IG Metall immediately organized temporary walkouts and stoppages all around Germany.
Among the sites hit were a factory of automaker Daimler in Bremen and plants belonging to Mercedes and ArcelorMittal in Hamburg in the north, a Ford site in Cologne and an Audi factory in Ingolstadt in the south of the country.
Plants belonging to car parts maker Continental, truck manufacturer MAN and French group Alstom would also be hit during the course of Friday, an IG Metall spokesman said.
A wage agreement between the union and the employers' federation Gesamtmetall expired in March.
Since then, both sides have been negotiating to reach a new deal for a sector that covers around 3.4 million employees in a wide range of engineering industries.
IG Metall is demanding pay increases of five percent in view of the comfortable profit situation in many companies in the sector.
It has rejected Gesamtmetall's offer of a pay rise of 2.1% over a two-year period.
Wage negotiations in the metalworking industry act as a benchmark for most other sectors.
IG Metall regularly stages so-called warning strikes to flex its muscles, but has not called an all-out strike since 2002.
Copyright Agence France-Presse, 2016