FRANKFURT (REUTERS) - Workers at Amazon.com Inc's German operations plan to continue their strikes next year, the Verdi labour union said on Friday, in a dispute over pay that has already been raging for several months.

"We will continue to strike, also next year," Verdi representative Joerg Lauenroth-Mago said. "But I won't say when and where exactly that will happen."

Hundreds of workers in Amazon's logistic centres in Bad Hersfeld and Leipzig have been on strike since Monday, in actions due to end on Saturday, Dec 21, threatening to disrupt shipments in the Christmas shopping season. Some staff at the company's Graben site have also stopped work.

Amazon said earlier this week 1,115 staff had joined the strikes at the three sites, but said there had been no delays to deliveries. The company employs a total of 9,000 warehouse staff in Germany plus 14,000 seasonal workers at nine distribution centres.

The German union has organised short strikes this year to try to force Amazon to accept collective bargaining agreements in use elsewhere in the mail order and retail industry, as benchmarks for pay at Amazon's German distribution centres.

However, Amazon has maintained that it regards staff at its centres in the cities of Bad Hersfeld and Leipzig as logistics workers and that they receive above-average pay by the standards of that industry.

Verdi members called their latest stoppages this week in the busy days before Christmas, when it would hurt the online retailer the most. Customers in Germany have in the past ordered almost 4 million items per day from Amazon at peak times, or 45 per second.