Workers went on strike at German sites of Amazon Monday to increase pressure on the US online retail giant during the busy Christmas period in a long-running pay dispute.
Around 2,300 employees took part in the work stoppage at five of the company's nine distribution centres in Germany, the services sector union Verdi said.
The strike, which is due to continue until Wednesday evening, will extend to a sixth site from Tuesday, it said in a statement, calling Monday's turnout a "great success".
"The employees are increasing the pressure on Amazon," Verdi's Stefanie Nutzenberger said, accusing Amazon of a "blockade attitude".
Amazon said it would still deliver on time and pointed out that only a minority of employees were taking part.
Verdi wants Amazon to bring the pay of 9,000 workers in Germany in line with wages in the mail order and retail industry.
Amazon has argued that its centres are logistics sites and that it pays its staff accordingly.