Internet payments company PayPal stopped doing business with WikiLeaks after receiving a letter from the US government, a senior executive has said.
Vice-president Osama Bedier told a conference the State Department had informed the company that the activities of the whistle-blowing website were illegal in the US, the BBC reports.
However, a State Department official denied on Twitter that it had contacted Paypal. US Assistant Secretary of State for Public Affairs Philip Crowley tweeted: "The US government did not write to PayPal requesting any action regarding #WikiLeaks. Not true."
WikiLeaks has angered the US and other governments by releasing hundreds of classified US diplomatic cables, and has said the arrest of its founder Julian Assange on charges of sexual assault would not stop it releasing more of the 250,000 documents it had obtained.
PayPal suspended payments to Wikileaks last week, and has been followed by Visa Europe and Mastercard.
Meanwhile, the Mastercard website has come under attack from hackers angry that it has suspended its relationship with Wikileaks.