Amazon warehouses in several European countries hit with Prime Day strike action over salaries and benefits.

Thousands of Amazon employees in Europe are striking over salaries and benefits in a move that coincides with Prime Day, the US online retail giant’s biggest annual shopping event.

On Tuesday, workers at six Amazon warehouses in Germany walked out, joining those already taking industrial action in Spain and Poland.

Germany’s Verdi services union called the one-day strike to demand better contracts and a guarantee of healthy working conditions.

“The message is clear – while the online giant gets rich, it is saving money on the health of its workers,” Verdi spokeswoman Stefanie Nutzenberger said in a statement.

Amazon employs around 16,000 workers in Germany and has refused to enter into collective wage negotiations with Verdi since 2013.

Jeff Bezos, founder and CEO of Amazon, is the world’s richest person [File: Joshua Roberts/Reuters]

In Spain, nearly 2,000 employees began a three-day strike on Monday.

The Spanish Workers’ Commissions (CCOO) and General Workers’ Union (UGT) said nearly 80 percent of workers left their positions at Amazon’s largest packing and distributing centre in the country. However, Amazon rejected the figure as inaccurate, saying the majority of employees did not take part in the strike.

Unai Sordo, CCOO’s secretary-general, said in a Twitter post on Monday that Amazon must resume negotiations and guarantee the workers’ “unquestionable rights”.

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Meanwhile, in Poland workers are staging a work to rule, with employees reporting for duty but doing the bare minimum of work required.

Amazon said the industrial actions would have no effect on Prime Day deliveries.

The strike action comes as it was announced that the net worth of Jeff Bezos, Amazon founder and chief executive, rose to more than $150bn on Monday.

Bezos is currently the world’s richest person, according to the Bloomberg Billionaires Index.

Monday also saw Amazon’s market capitalisation rise to $888bn, making it the world’s second-most valuable company after tech giant Apple, valued at $940bn.