Dutch police have arrested a 16-year-old boy for online attacks on MasterCard and PayPal, as the digital guerrilla warfare between WikiLeaks’ supporters and its opponents escalated.

Anonymous, the loose group of internet campaigners that has been supporting WikiLeaks, claimed credit for disrupting the websites of MasterCard, Visa and PayPal on Wednesday and Thursday, but was frustrated in its attempt to take down Amazon’s site, in spite of threatening the retailer with a “denial of service attack”.

However, WikiLeaks’ site is still being bombarded by cyber-assaults following its mass release of confidential US documents. Facebook and Twitter removed social-networking profiles operated by Anonymous, which has made revenge attacks against services its supporters accuse of abandoning Wiki-Leaks in recent days.