BERLIN - A German trade union called on workers at seven Amazon warehouses to go on strike on Tuesday to coincide with the global "Prime Day" promotion event that was postponed due to operational challenges from the coronavirus pandemic.

Verdi said it was organising the two-day strike as part of a long-running battle with Amazon in Germany over better pay and conditions, noting that a coronavirus bonus introduced for workers in Germany in March had been scrapped again in May.

An Amazon spokesman said the majority of employees were continuing to work as normal despite the strike call. He said the company offered "excellent salaries", with benefits and working conditions comparable with other important employers.

Verdi has been organising strikes at Amazon in Germany since 2013, most recently in June in protest over safety after some staff at logistics centres tested positive for the coronavirus.

Germany is Amazon's biggest market after the United States.

Prime Day, typically held in July to boost summer sales, is now a kickoff to what will be an earlier holiday shopping season. The member-only discounts are a key way Amazon markets Prime, a fast-shipping and media-streaming service that incentivises subscribers to do more shopping on Amazon. 

A report by news site Reveal said the week around last year's Prime Day was the most dangerous for injuries at Amazon's fulfillment centers, prompting criticism by a prominent union. Amazon disputed the claims.

(Reporting by Matthias Inverardi and Emma Thomasson; Editing by Kirsten Donovan) ((Reuters Messaging: emma.thomasson.thomsonreuters.com@reuters.net))