EBay Inc. (EBAY.O) sued e-commerce rival Amazon.com Inc. (AMZN.O), claiming the world’s largest online retailer infiltrated EBay’s internal email system to recruit high-value sellers

Amazon’s illegal efforts "appear to be part of a larger pattern of aggressive, unscrupulous conduct," according to the complaint filed Wednesday in state court in San Jose, California.

Amazon, through a spokeswoman, declined to comment. The company has said it was investigating EBay’s allegations, which came to light this month after the internet marketplace’s lawyers sent a cease-and-desist letter to Amazon.

EBay has accused Amazon of poaching sellers on its site around the world by infiltrating and using EBay’s member-to-member email system. The San Jose-based company said the alleged practice violates its terms of service.

EBay and Amazon are fierce competitors that rely on independent merchants who sell on their sites. Amazon has more customers, sales and faster growth than EBay, but some sellers prefer the EBay platform since it is a pure marketplace, meaning EBay doesn’t compete with its merchants for sales like Seattle-based Amazon.

The lawsuit includes claims for interference with contractual relations and violations of California’s penal code and business and professions code. EBay seeks monetary damages as well as a court order barring Amazon from poaching EBay’s member-sellers.

The case is eBay Inc. v. Amazon.com Inc., 18cv336315, California Superior Court, Santa Clara County (San Jose).