Employees of Amazon take part in a strike organized by Ver.di in front of an Amazon warehouse in Bad Hersfeld May 14, 2013. The union and Amazon have been at odds over how to define the company's order-fulfillment workers. The online retailer says they work logistics while the union says they're in the mail order and retail industry. Reuters

Members of one of Germany’s largest trade unions began a two-day strike Friday at two Amazon.com facilities amid wage negotiations that hinge on whether employees at the company’s distribution centers are considered retailers or logistics workers.

The United Services Union, known by its German abbreviation Ver.di, said Thursday that work would be interrupted at two Amazon distribution centers through Saturday. Employees at Amazon’s facility in the central town of Bad Hersfeld began their strike late Thursday, while their counterparts in Leipzig, 160 miles to the east, began their strike Friday morning.

“Amazon refusing to speak about a collective [bargaining] agreement shows a lack of respect and lack of appreciation for the performance of its employees,” Stefanie Nutzenberger, Ver.di board member, said in a statement Thursday announcing the labor action against the world’s largest online retailer.

Amazon has faced a series of labor problems in Germany, its largest market outside the United States. In December workers at the Bad Hersfeld facility walked off the job for four days during the peak holiday season, demanding the right to collective bargaining. The two sides have been at odds over the definition of an Amazon distribution-center employee. The union says these workers are covered by agreements affecting the mail order and retail industry, while the company says these workers are involved in logistics.

“Our people stow, pick and pack,” a spokesperson for Amazon in Germany told the Financial Times. “It is not like Harrods where you have customers in front of you and need a special level of education to do that."

Ver.di said Amazon’s distribution-center workers should have received a 5.5 percent pay hike last year that was the result of a collective bargaining agreement affecting the country’s mail order and retail workers. Instead, the workers received a 2 percent pay hike last year. Amazon says its warehouse employees receive wages that are higher than the average for warehouse employees in Germany.

The Seattle online retailer employs about 9,000 permanent workers and 14,000 seasonal temps in Europe’s largest economy.