A trade union has called on workers at an Amazon warehouse in Germany to hold their second strike in a week in an effort to disrupt Black Friday order processing, Reuters reported. Some 500 workers took part in a three-day strike that started Thursday and ended Saturday, according to trade union Verdi, with the next strike set to begin Monday night and end Tuesday night. Germany is Amazon’s second-biggest market after the US.

Amazon workers at six sites across Germany struck in June to protest safety at its logistics centers, where dozens of workers had become infected with the coronavirus. Warehouse workers in Germany have struck against Amazon several times in recent years to protest workers’ pay and conditions.

The strikes in Germany are separate from a larger, international protest by climate activists and Amazon warehouse workers that launched on Black Friday. The “Make Amazon Pay,” campaign called on Amazon to provide better working conditions for its employees and to reduce its carbon footprint.

Amazon has come under intense criticism during the coronavirus pandemic. Its net income nearly tripled in the third quarter, to $6.33 billion. But Amazon workers have staged protests because they say the e-commerce firm has not taken the dangers of the coronavirus seriously. Some 19,816 of Amazon’s front-line workers have contracted the virus, the company said last month.

On Thanksgiving, Amazon announced holiday bonuses for its workers: $300 for full-time workers and $150 for part-timers.

Amazon did not immediately reply to a request for comment Sunday.