German union Verdi on Sunday called on workers at Amazon warehouses to join strikes in coming days.

The union did not state exactly when the strikes will be held.

What do we know about the strikes?

Verdi said that it had called on workers at seven German distribution centers to engage in strikes that would alternate between different locations. It said that alternating strikes would hinder management's attempts to prepare for stoppages.

It said it had urged workers to stop work at dispatch centers in Bad Hersfeld, Dortmund, Graben near Augsburg, Koblenz, Leipzig and Werne.

"Colleagues are furious and don't want to be taken for fools by a company that makes billions in profits," Verdi said in a statement.

Verdi cited the lack of a collective bargaining as one of the reasons for the action, as well as low Christmas and holiday pay.

"This is especially urgent during the intense Christmas sales period, when employees have to push themselves to their physical limits," the union stressed, adding that it was protesting what it called Amazon's "antisocial practices."

Amazon said it does not expect the strikes to have an impact on costumers. While the retail giant said that it had raised salaries for Amazon employees in logistics earlier this year, Verdi has argued that these increases are well below the rate of inflation.

Nearly a decade of strikes

Germany is Amazon's biggest market after the United States. Verdi has been organizing strikes at Amazon's German sites since 2013.

Amazon does not recognize collective bargaining agreements in Germany.

Verdi said that Amazon staff in Germany earned several thousand euros less per year than counterparts at companies with collective bargaining rights.

sdi/dj (Reuters, AFP, dpa)