The warning strikes in several hundred metal plants in the south western region of Baden-Württemberg began overnight and continued throughout the day, a union spokesman said.
Important talks are scheduled for Wednesday in Baden Württemberg and on Thursday in Bavaria, when it will become clear whether an agreement can be reached to stave off what would be the industry's first full-scale strikes in 11 years.
The industrial action came ahead of Monday afternoon's fourth round of negotiations in which the union is demanding 5.5-percent salary rise this year for 3.7 million metalworkers spread across different branches ranging from automobiles to electronics.
Accompanying warning strikes also occurred in other regions including North-Rhine Westphalia and Bavaria, as negotiations with the same demands were due to enter their third rounds.
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