Some of Amazon’s (NASDAQ:AMZN) workers in Europe chose one of the biggest shopping days of the year to protest the company’s practices. Black Friday is a US tradition that has been embraced by Europeans in recent years. Retailers like Amazon offer large discounts on clothing, electronics and toys during the shopping holiday.

Amazon employees were striking at six distribution centers in Germany on Friday. The strikes took place at major depots in Bad Hersfeld, Leipzig, Rheinberg, Werne, Graben, and Koblenz. Germany is Amazon’s second-biggest market after the United States. Amazon employs 11,000 warehouse staff in the country, along with thousands of seasonal workers.

The strikes are part of a long-running dispute over pay and conditions for the company’s workers in the country. German services’ sector union Verdi has organized frequent strikes at Amazon since May 2013. Verdi board member Stefanie Nutzberger said in a statement, “Amazon permanently endangers the health of its employees with its way of working. High pressure to create more and more in less time, permanent performance controls and monitoring, a poor leadership culture and inadequate recovery times are health hazards in the Amazon labor process.”

Verdi also said Amazon was refusing to pay their employees fair wages. The employees are demanding the retailer raise pay for warehouse workers in accordance with collective bargaining agreements in Germany’s mail order and retail industries. The company has repeatedly rejected the union’s demands, saying warehouse staff should be paid in line with employees in the logistics sector, not as retail staff. The company said salaries paid to its workers were among the highest in the logistic sector.

Workers at Amazon’s main distribution hub in Italy also planned to walk out on Friday. Several Italian labor unions said in a joint statement that more than 500 Amazon staff at the Piacenza site in northern Italy would be striking. Workers have also decided to reject any overtime until December 31. Amazon employs around 4,000 workers at Piacenza during the pre-Christmas season.

In a statement, Amazon said it was “focused on maintaining delivery times for Black Friday and the following days.” A company spokesperson said, “The vast majority of our employees in Italy and Germany came to work and remained focused on delivering the best customer experience. We are proud of our record of job creation and are confident we will deliver for our customers this holiday season.”