Employees of the internet giant Amazon are taking strike action in Germany in a long-running pay dispute.

The Verdi union said workers were on strike at Amazon's logistic centres in Bad Hersfeld and Leipzig and also in Graben. The action coincides with the busy Christmas shopping period.

Amazon employs more than 9,000 workers in Germany.

Later on Monday, a delegation of German workers will also protest at Amazon's headquarters in Seattle.

The union is planning further action on Tuesday in Germany in the town of Werne.

Amazon said 640 workers expected on the early shift had failed to turn up for work and that the industrial action would have little or no impact on orders: "Our customers can continue to rely on us for the prompt delivery of their Christmas presents," said a spokeswoman told Reuters.

The union said up to 700 workers joined the strike in Bad Hersfeld and another 200 had taken action in Leipzig.

The Verdi union added that action at the Graben site - the first strike at that plant - had been well supported.

Classification row

Amazon's sales in Germany are growing fast. Last year, they rose by 21% and the country is the firm's second-biggest market after the US, responsible for about a third of all overseas sales.

Verdi has called a series of strikes this year in an attempt to get the company to accept collective bargaining agreements for its staff.

It says Amazon is not paying them comparable rates to other warehouse staff in Germany, because the company has classified the staff as logistics workers, whose rates of pay are lower.

Verdi said in a statement: "The Amazon system is characterised by low wages, permanent performance pressure and short-term contracts."

Amazon says that they are well paid compared with other logistics workers in the country.

The union is also unhappy with what it calls the company's practice of "constant monitoring" of workers and what it says are impossible workplace targets.

Last month, an investigation by the BBC's Panorama programme into a UK-based Amazon warehouse found conditions a stress expert said could cause "mental and physical illness".

Prof Michael Marmot was shown secret filming of night shifts involving up to 11 miles of walking at the warehouse - where an undercover worker was expected to collect orders every 33 seconds.

Amazon told the BBC in a statement that worker safety was its "number one priority".