WikiLeaks said early Saturday that it was suing the European operations of Visa and MasterCard because they cut off services to the secrets-spreading website last December.
A statement tweeted from WikiLeaks said WikiLeaks and service provider Datacell would sue the credit card companies, alleging that they engaged "in an unlawful, U.S. influenced, financial blockade."
The statement accused the companies of coordinating to block donation payments to WikiLeaks in December and violating European Union competition laws. The statement said a complaint would be filed with the European Commission.
"Further actions in other jurisdictions will follow," the statement said.
Visa, MasterCard and PayPal cut off the flow of donations to WikiLeaks because of legal concerns over how it obtained secret documents that it disseminated on the Internet last fall.
After a crush of traffic prompted WikiLeaks to move from a Swedish base to Amazon.com servers, U.S. congressional staffers put pressure on the Internet retailer, and it also shut down the WikiLeaks site on its servers for distributing documents it didn't own.
PayPal and Amazon.com were not mentioned in the statement.
Pro-WikiLeaks hackers struck against companies that had cut their ties to WikiLeaks, managing to take down the websites of MasterCard and Visa, but the attack was seen as ineffective.
WikiLeaks founder Julian Assange is under house arrest in England while he fights sexual assault allegations.