Facebook and Twitter deleted the accounts of cyber activists who targeted Visa and other Internet payment sites that sought to block the WikiLeaks website after its release of U.S. diplomatic cables.

Facebook confirmed it had removed the activists’ Operation Payback site on Thursday because it was promoting a distributed denial of service attack — an illegal form of freezing websites. Twitter declined to comment.

The swoop against Operation Payback’s self-described “campaigners for Internet freedom” followed their online attacks on credit-card giants like Visa and MasterCard.

The campaign reappeared on Twitter later in the European afternoon using another account. Experts said outages were unlikely to have much effect on the pro-WikiLeaks cyber campaign, as activists were using separate chat-rooms to organize.