A delegation of German workers is also set to protest at Amazon's headquarters in Seattle, in the US with the help of American labor unions, Verdi said.

In addition, the union walkout in Germany is to spread to a distribution center in Werne on Tuesday.

The German union has launched a series of industrial action against Amazon this year in support of a demand that the firm accepted a collective bargaining agreement for the mail order and retail sectors as benchmark for workers' pay. Amazon, however, regards its staff as logistics workers who are normally lower-paid but receive above-average wages by the standards of that sector.

"Amazon's remuneration system is marked by low wages and permanent pressure as a result of temporary work contracts," senior Verdi representative Stefanie Nutzenberger said.

Especially in the Christmas season, workers were doing a great job and would deserve being paid like mail order and retail workers, she told reporters.

Amazon, which employs about 9,000 workers in 8 logistics centers in Germany, has repeatedly refused to enter into wage negotiations with Verdi.

uhe/mz (Reuters, dpa, AFP)