A group of more than 2,000 online sellers has filed an antitrust case against Amazon in India, alleging the US company favors some retailers whose online discounts drive independent vendors out of business, a legal filing seen by Reuters showed.

The case presents a new regulatory challenge for Amazon in India, where it has committed $6.5 billion in investment but is battling a complex regulatory environment.

In January, the Competition Commission of India (CCI) had ordered an investigation of Amazon and rival Flipkart, owned by Walmart, over alleged violations of competition law and certain discounting practices, which Amazon is challenging, according to court filings.

In the latest case, the All India Online Vendors Association, members of which sell goods on Amazon and Flipkart, allege Amazon engages in unfair business practices. Reuters was first to report the case filing on Wednesday.

The group alleges that Amazon India’s wholesale arm buys goods in bulk from manufacturers and sells them at a loss to sellers such as Cloudtail. Such sellers then offer goods on Amazon.in at big discounts.

Amazon said in a statement it complies with all laws and its India website is a pure third-party marketplace where sellers have discretion to decide product prices. Amazon’s statement also said its wholesale unit allows businesses to buy products and anyone can register on it.