The online payments processor, PayPal, says it has cut access for donations to the whistle-blowing website Wikileaks.
PayPal said its payment service cannot be used for activities "that encourage, promote, facilitate or instruct others to engage in illegal activity".
Wikileaks' latest releases - of US diplomatic cables - have caused considerable embarrassment to the US and its allies, correspondents say.
It has been forced to change its web address after sustained cyber attacks.
In a statement, US-based PayPal said donations could no longer be made to Wikileaks because of "a violation of the PayPal Acceptable Use Policy"
Earlier, the company providing Wikileaks with its domain name, EveryDNS.net, cut off service because the domain wikileaks.org had become the target of "multiple distributed denial of service (DDOS) attacks".
The company said: "These attacks have, and future attacks would, threaten the stability of the EveryDNS.net infrastructure, which enables access to almost 500,000 other websites."
Wikileaks later reappeared using a Swiss web address.
It had earlier turned to the online store Amazon to host its site but the company ended the agreement on Wednesday - a move welcomed by US officials.
Amazon said Wikileaks had failed to adhere to its terms of service.
"It's clear that Wikileaks doesn't own or otherwise control all the rights to this classified content. Further it is not credible that the extraordinary volume of 250,000 classified documents that Wikileaks is publishing could have been carefully redacted in such a way as to ensure that they weren't putting innocent people in jeopardy," Amazon said on its website.