SOPA Images

As two of the top e-commerce sites, Amazon and eBay are constantly competing to bring on top sellers to their sites. But, eBay is accusing Amazon of going too far in that battle.

eBay on Wednesday said its rival pulled together an international, coordinated and illegal effort to target eBay's best sellers and move them over to Amazon's site.

"We have uncovered an unlawful and troubling scheme on the part of Amazon to solicit eBay sellers to move to Amazon's platform," an eBay spokesperson said in a statement. "We have demanded that Amazon end its unlawful activity and we will take the appropriate steps, as needed, to protect eBay."

On Monday, eBay sent a cease and desist order to Amazon after it said it uncovered evidence -- going back years -- of the alleged poaching scheme.

An Amazon spokesperson said in a statement: "We are conducting a thorough investigation of these allegations."

Both Amazon and eBay allow third-party sellers to list and sell items on their sites. These sellers are critical to both businesses, since the companies make billions of dollars in commissions on these sales. Amazon says third-party sellers account for more than half of its retail sales. These outside sellers account for all of eBay's retail sales.

If true, eBay's accusations against Amazon could result in fines or new restriction on Amazon, since eBay claims Amazon broke the law in its effort to poach eBay sellers. eBay claims Amazon violated the California Comprehensive Computer Data Access and Fraud Act.

eBay says it was alerted to the scheme about 10 days ago, after an eBay seller told the company about being contact by an Amazon employee. eBay says it soon after found Amazon workers had been using the messaging system on eBay's website to contact and try poaching eBay sellers.

eBay claims Amazon workers intentionally hid their tracks in the messages by obscuring their email addresses and the name of their company, which could've triggered eBay's monitoring system.

The Wall Street Journal earlier reported on the alleged scheme.

NASA turns 60: The space agency has taken humanity farther than anyone else, and it has plans to go further.

Taking It to Extremes: Mix insane situations -- erupting volcanoes, nuclear meltdowns, 30-foot waves -- with everyday tech. Here's what happens.