Amazon forces third-party sellers who use its platform to keep prices within limits that the tech giant sets, the Federal Cartel Office said in a statement, reducing the visibility of products that do not keep to its rules or even removing them entirely.

"Since Amazon competes directly with other marketplace retailers on its platform, influencing competitors' pricing, including in the form of price caps, is highly questionable," said Andreas Mundt, head of the regulator.

"That is especially so when the traders concerned cannot cover their own costs."

Amazon, which according to the cartel office accounts for about 60 percent of online retail revenue in Germany, now has the opportunity to respond to the regulator's preliminary ruling.

A spokeswoman for Amazon said it strongly disputed the cartel office's findings and that its rules helped its customers.

"Shopping on Amazon is designed so that customers who visit our store can trust that they will find the best deal based on price, availability and speed of delivery," the spokeswoman said.

"That is why they keep coming back."

Amazon is facing other allegations of anti-competitive behaviour, with US regulators accusing the online giant of preventing sellers from offering products at lower prices on other platforms.

Germany's cartel office began investigating Amazon's pricing rules in November 2022.